ME1260-Engineer's Guide to Cross Connection Control · The Engineer's Guide to Cross Connection Control course satisfies four (4) hours of professional development. The course is

Approved Continuing Education for Licensed Professional Engineers

Engineer's Guide to Cross Connection Control

Four (4) Continuing Education Hours Course #ME1260

EZ-pdh.com Ezekiel Enterprises, LLC

301 Mission Dr. Unit 571 New Smyrna Beach, FL 32170

800-433-1487 [email protected]

https://ez-pdh.com/

Engineer's Guide to Cross Connection Control Ezekiel Enterprises, LLC

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Course Description:

The Engineer's Guide to Cross Connection Control course satisfies four (4) hours of professional development.

The course is designed as a distance learning course that overviews the importance of cross connection control and methods to mitigate contamination risks.

Objectives:

The primary objective of this course is to enable the student to understand cross connection risks, review real case studies of cross connection mishaps, and understand the various methods and procedures to mitigate cross connection hazards.

Grading:

Students must achieve a minimum score of 70% on the online quiz to pass this course. The quiz may be taken as many times as necessary to successful pass and complete the course.

A copy of the quiz questions are attached to last pages of this document.

Engineer's Guide to Cross Connection Control Ezekiel Enterprises, LLC

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Table of Contents Engineer's Guide to Cross Connection Control

Chapter 1: Purpose & Scope .................................................... 1

Chapter 2: Public Health Significance of Cross-Connections ...... 2

Chapter 3: Theory of Backflow and Backsiphonage ................ 12

Chapter 4: Methods and Devices for the Prevention of Backflow

and Backsiphonage .............................................. 16

Chapter 5: Testing Procedures for Backflow Preventers .......... 25

Chapter 6: Administration of a Cross-Connection Control

Program .............................................................. 30

Chapter 7: Cross-Connection Control Ordinance Provisions ... 33

Appendix A: Partial List of Plumbing Hazards ............................. 38

Appendix B: Illustrations of Backsiphonage ............................... 38

Appendix C: Illustrations of Backpressure .................................. 40

Appendix D: Illustrations of Air Gaps ......................................... 41

Appendix E: Illustrations of Vacuum Breakers ............................ 41

Appendix F: Glossary ................................................................ 42

Quiz Questions ..................................................... 43

CHAPTER ONE • 1

Chapter One

Public health officials havelong been concerned

about cross-connections andbackflow connections inplumbing systems and in publicdrinking water supply distribu-tion systems. Such cross-connections, which makepossible the contamination ofpotable water, are ever-presentdangers. One example of whatcan happen is an epidemic thatoccurred in Chicago in 1933.Old, defective, and improperlydesigned plumbing and fixturespermitted the contamination ofdrinking water. As a result.1,409 persons contractedamebic dysentery; there were98 deaths. This epidemic, andothers resulting from contami-nation introduced into a watersupply through improperplumbing, made clear theresponsibility of public healthofficials and water purveyors forexercising control over publicwater distribution systems andall plumbing systems connectedto them. This responsibilityincludes advising and instruct-ing plumbing installers in therecognition and elimination ofcross-connections.

Cross-connections are thelinks through which it ispossible for contaminatingmaterials to enter a potablewater supply. The contaminantenters the potable water systemwhen the pressure of thepolluted source exceeds thepressure of the potable source.The action may be calledbacksiphonage or backflow.Essentially it is reversal of thehydraulic gradient that can beproduced by a variety ofcircumstances.

It might be assumed thatsteps for detecting and elimi-nating cross-connections wouldbe elementary and obvious.Actually, cross-connections mayappear in many subtle formsand in unsuspected places.Reversal of pressure in thewater may be freakish andunpredictable. The probabilityof contamination of drinkingwater through a cross-connection occurring within asingle plumbing system mayseem remote; but, consideringthe multitude of similarsystems, the probability isgreat.

Why do suchcross-connectionsexist?

First, plumbing is frequentlyinstalled by persons who areunaware of the inherentdangers of cross-connections.Second, such connections aremade as a simple matter ofconvenience without regard tothe dangerous situation thatmight be created. And, third,they are made with reliance oninadequate protection such as asingle valve or other mechanicaldevice.

To combat the dangers ofcross-connections and backflowconnections, education in theirrecognition and prevention isneeded. First, plumbinginstallers must know thathydraulic and pollutionalfactors may combine to producea sanitary hazard if a cross-connection is present. Second,they must realize that there areavailable reliable and simple

standard backflow prevention devices and methods that may be substituted for the conve-nient but dangerous direct connection. And third, it should be made clear to all that the hazards resulting from direct connections greatly outweigh the convenience gained. This course does not describe all the cross-connections possible in piping systems. It does attempt to reduce the subject to a statement of the principles involved and to make it clear to the reader that such installa-tions are potentially dangerous. The primary purpose is to define, describe, and illustrate typical cross-connections and to suggest simple methods and devices by which they may be eliminated without interfering with the functions of plumbing or water supply distribution systems.

Purposeand Scope

Chapter Two

Public health officials havelong been aware of the

impact that cross-connectionsplay as a threat to the publichealth. Because plumbingdefects are so frequent andthe opportunity for contami-nants to invade the publicdrinking water through cross-connections are so general,enteric illnesses caused bydrinking water may occur atmost any location and at anytime.

The following documentedcases of cross-connectionproblems illustrate andemphasize how actual cross-connections have compromisedthe water quality and the publichealth.

Human Blood inthe Water System

Health Department officialscut off the water supply to

a funeral home located in alarge southern city, after it wasdetermined that human bloodhad contaminated the freshwater supply. City water andplumbing officials said that theydid not think that the bloodcontamination had spreadbeyond the building, however,inspectors were sent into theneighborhood to check forpossible contamination. Thechief plumbing inspector hadreceived a telephone calladvising that blood was comingfrom drinking fountains withinthe building. Plumbing andcounty health departmentinspectors went to the sceneand found evidence that theblood had been circulating inthe water system within thebuilding. They immediatelyordered the building cut offfrom the water system at themeter.

Public HealthSignificance ofCross-Connections

Investigation revealed thatthe funeral home had beenusing a hydraulic aspirator todrain fluids from the bodies ofhuman “remains” as part of theembalming process. Theaspirator directly connected tothe water supply system at afaucet outlet located on a sinkin the “preparation” (embalm-ing) room. Water flow throughthe aspirator created suctionthat was utilized to draw bodyfluids through a hose andneedle attached to the suctionside of the aspirator.

The contamination of thefuneral home potable watersupply was caused by a combi-nation of low water pressure inconjunction with the simulta-neous use of the aspirator.Instead of the body fluidsflowing into the sanitary drain,they were drawn in the oppositedirection—into the potablewater supply of the funeralhome!

Reverse flow throughaspirator due toback siphonage

Body fluids

“Hydro”aspirator

Negative supply pressureOpen

Closed

Closed

Normal operationPositive supply pressure Potable water Open

2 • ENGINEER'S GUIDE TO CROSS CONNECTION CONTROL

Burned in theShower

One neighbor’s head wascovered with blisters after shewashed her hair and otherscomplained of burned throatsor mouths after drinking thewater.

The incident began after an8-inch water main, that fed thetown, broke and was repaired.While repairing the watermain, one workman sufferedleg burns from a chemical inthe water and required medicaltreatment. Measurements of theph of the water were as high as13 in some sections of the pipe.

Investigation into the causeof the problem led to a possiblesource of the contaminationfrom a nearby chemicalcompany that distributeschemicals such as sodiumhydroxide. The sodium hydrox-ide is brought to the plant inliquid form in bulk tankertrucks and is transferred to aholding tank and then pumpedinto 55 gallon drums. Whenthe water main broke, a truckdriver was adding the waterfrom the bottom of the tanktruck instead of the top, andsodium hydroxide back-siphoned into the water main.

Heating SystemAnti-Freeze intoPotable Water

A resident of a small town inAlabama, jumped in the

shower at 5 a.m. one morningin October, 1986, and when hegot out his body was coveredwith tiny blisters. “The more Irubbed it, the worse it got,” the60 year old resident said. “Itlooked like someone took ablow torch and singed me.”

He and several otherresidents received medicaltreatment at the emergencyroom of the local hospital afterthe water system was contami-nated with sodium hydroxide, astrong caustic solution.

Other residents claimedthat, “It (the water) bubbled upand looked like Alka Seltzer. Istuck my hand under the faucetand some blisters came up.”

Chemical bulk storage and holding tanks

“Burned in the shower”

Water mainbreak andrepair

water service Hose with bottom fill

Automobile antifreezeadded to boiler water

Backsiphonage(reverse flow)

Normal flow

Curb stop with stopand waste drain

Water main

Bangor Maine WaterDepartment employees

discovered poisonous antifreezein a homeowner’s heatingsystem and water supply inNovember, 1981. The incidentoccurred when they shut off‘the service line to the home tomake repairs. With the flow ofwater to the house cut off,pressure in the lines in thehouse dropped and the anti-freeze, placed in the heatingsystem to prevent freeze-up ofan unused hot water heatingsystem, drained out of theheating system into housewater lines, and flowed out tothe street. If it had not beennoticed, it would have enteredthe homeowner’s drinkingwater when the water pressurewas restored.

CHAPTER TWO • 3

Salt water suction linefor fire protection

Main freshwater line

Pump prime line

High pressure fire lineSeawater

Backflow preventerreplaced by spool piece

Mixing Sink

Herbicide holding tank

Potable town water

Recommended installation ofbackflow preventer

Salty Drinks Paraquat in theWater System

water supply piping had beenleft open. A lethal cross-connection had been createdthat permitted the herbicide toflow into the potable watersupply system. Upon restora-tion of water pressure, theherbicides flowed into the manyfaucets and outlets on the townwater distribution system.

This cross-connectioncreated a needless and costlyevent that fortunately did notresult in serious illness or loss oflife. Door-to-door publicnotification, extensive flushing,water sample analysis, emer-gency arrangements to providetemporary potable water fromtanker trucks, all contributed toan expensive and unnecessarytown burden.

In January, 1981, a nationallyknown fast food restaurant

located in southeastern UnitedStates, complained to the waterdepartment that all their softdrinks were being rejected bytheir customers as tasting“salty.” This included sodafountain beverages, coffee,orange juice, etc. An investiga-tion revealed that an adjacentwater customer complained ofsalty water occurring simulta-neously with the restaurantincident. This second complaintcame from a water front shiprepair facility that was alsobeing served by the same watermain lateral. The (investigationcentered on the ship repairfacility and revealed thefollowing:

• A backflow preventerthat had been installed on theservice line to the shipyard hadfrozen and had been replacedwith a spool piece sleeve.

• The shipyard fireprotection system utilized seawater that was pumped by bothelectric and diesel drivenpumps.

• The pumps were primedby potable city water.

With the potable primingline left open and the pumpsmaintaining pressure in the firelines, raw salt water waspumped through the priminglines, through the spool sleevepiece, to the ship repair facilityand the restaurant.

“Yellow gushy stuff ”poured from some of

the faucets in a small town inMaryland, and the State ofMaryland placed a ban ondrinking the water supply.Residents were warned not touse the water for cooking,bathing, drinking or any otherpurpose except for flushingtoilets.

The incident drew wide-spread attention and made thelocal newspapers. In addition tobeing the lead story on theABC news affiliate in Washing-ton, D.C. and virtually all theWashington/Baltimore news-papers that evening. The newsmedia contended that lethalpesticides may have contami-nated the water supply andamong the contaminants wasparaquat, a powerful agricul-tural herbicide.

The investigation disclosedthat the water pressure in thetown water mains was tempo-rarily reduced due to a waterpump failure in the town watersupply pumping system.Coincidentally, a gate valvebetween a herbicide chemicalholding tank and the town


Recommended installationof hose bibb vacuum breakerbackflow preventer

Gate valve closed

Recommendedbackflowpreventer

installation

Water mainpressure65 psi

Explosion

FireHose used for propane tankpurging cross

connectedto private

fire hydrant

Propane Gas in theWater Mains

ate repair procedures. Tostart the repair, the tank was“purged” of residual propaneby using water from one of twoprivate fire hydrants located onthe property. Water purgingis the preferred method ofpurging over the use of carbondioxide since it is more positiveand will float out any sludge aswell as any gas vapors. The“purging” consisted of hookingup a hose to one of the privatefire hydrants located on theproperty and initiating flushingprocedures.

Since the vapor pressure ofthe propane residual in the tankwas 85 to 90 psi., and the waterpressure was only 65 to 70 psi.,propane gas backpressurebackflowed into the watermain. It was estimated that thegas flowed into the water mainsfor about 20 minutes and thatabout 2,000 cubic feet of gaswas involved. This was approxi-mately enough gas to fill onemile of an 8-inch water main.

Chlordane andHeptachlor at theHousing Authority

of the gate valve. When theworkman cut the 6-inch line,water started to drain out of thecut, thereby setting up abacksiphonage condition. As aresult, the chemicals weresiphoned out of the truck,through the garden hose, andinto the system, contaminatingthe seventy five apartments.

Repeated efforts to cleanand flush the lines were notsatisfactory and it was finallydecided to replace the waterline and all the plumbing thatwas affected. There were noreports of illness, but residentsof the housing authority weretold not to use any tap waterfor any purpose and they weregiven water that was truckedinto the area by volunteer firedepartment personnel. Theywere without their normalwater supply for 27 days.

Hundreds of people wereevacuated from their

homes and businesses on anAugust afternoon in a town inConnecticut in 1982 as a resultof propane entering the citywater supply system. Fires werereported in two homes and thetown water supply was con-taminated. One five-roomresidence was gutted by a blazeresulting from propane gas“bubbling and hissing” from abathroom toilet and in anotherhome a washing machineexplosion blew a womanagainst a wall. Residentsthroughout the area reportedhissing, bubbling noises,coming from washingmachines, sinks and toilets.Faucets sputtered out smallstreams of water mixed withgas and residents in the areawere asked to evacuate theirhomes.

This near-disaster occurredin one, 30,000 gallon capacityliquid propane tank when thegas company initiated immedi-

The services to seventy fiveapartments housing

approximately three hundredpeople were contaminated withchlordane and heptachlor in acity in Pennsylvania, in Decem-ber, 1980. The insecticidesentered the water supplysystem while an exterminatingcompany was applying them asa preventative measure againsttermites. While the pesticidecontractor was mixing thechemicals in a tank truck withwater from a garden hosecoming from one of theapartments, a workman wascutting into a 6-inch main lineto install a gate valve. The endof the garden hose was sub-merged in the tank containingthe pesticides, and at the sametime, the water to the area wasshut off and the lines beingdrained prior to the installation

CHAPTER TWO • 5

Boiler WaterEnters High SchoolDrinking Water

No students or facultywere known to have consumedany of the water; however, areaphysicians and hospitals advisedthat if anyone had consumedthose high levels of chromium,the symptoms would be nausea,diarrhea, and burning of themouth and throat. Fortunately,the home economics teacher,who first saw the discoloredwater before school started,immediately covered all waterfountains with towels so thatno one would drink the water.

Investigation disclosedthat chromium used in theheating system boilers to inhibitcorrosion of metal parts enteredthe potable water supplysystem as a result of backflowthrough leaking check valveson the boiler feed lines.

Pesticide inDrinking Water

Car Wash Waterin the Water MainStreet

A high school in NewMexico, was closed for

several days in June 1984 whena home economics teachernoticed the water in the potablesystem was yellow. Citychemists determined thatsamples taken contained levelsof chromium as high as 700parts per million, “astronomi-cally higher than the acceptedlevels of .05 parts per million.”The head chemist said that itwas miraculous that no one wasseriously injured or killed by thehigh levels of chromium. Thechemical was identified assodium dichromate, a toxicform of chromium used inheating system boilers to inhibitcorrosion of the metal parts.

A pesticide contaminated aNorth Carolina water

system in April, 1986, prompt-ing the town to warn residentsof 23 households not to drinkthe water. The residents in theaffected area were supplieddrinking water from a tanktruck parked in the parking lotof a downtown office buildinguntil the condition could becleared up. Residents com-plained of foul smelling waterbut there were no reports ofillness from ingesting the waterthat had been contaminatedwith a pesticide containingchlordane and heptachlor.

Authorities stated that theproblem occurred when a watermain broke at the same timethat a pest control service wasfilling a pesticide truck withwater. The reduction in pressurecaused the pesticide from insidethe tank to be sucked into thebuilding’s water main. Thepesticide contaminated thepotable water supply of theoffice building and neighbor-hood area.

This car wash cross-connection and back-

pressure incident, whichoccurred in February, 1979,in the state of Washington,resulted in backflow chemicalcontamination of approximately100 square blocks of watermains. Prompt response by thewater department prevented apotentially hazardous waterquality degradation problemwithout a recorded case ofillness.

Numerous complaints ofgrey-green and “slippery” waterwere received by the waterdepartment coming from thesame general area of town. Asample brought to the waterdepartment by a customerconfirmed the reported problemand preliminary analysisindicated contamination withwhat appeared to be a deter-gent solution. While emergencycrews initiated flushing opera-tions, further investigationwithin the contaminated areasignaled the problem wasprobably caused by a car wash,

Pump

Street

High SchoolWater cooler

Bubbler

Bubbler

Leaky check valves

High school boilers

Recommended installationof backflow preventer

Toxic rust inhibitor anddefoamant containingsodium dichromate

Recommended installationof hose bibb vacuum breakerbackflow preventer


Shipboardraw waterpumpingsystem

To washrooms

To washrooms

Potable water

supply

Cafeteria drinking fountainsand sanitation water

Reduced pressure principle backflow preventers should have been installed at dockside outlets and other locations

Potable supply hose

Wax injectors

To reclaim tanksScrubbers

Potable water supply

RinseRinse

Soap injectors

Hose connectionmade here

Recommendedinstallation ofbackflow preventer Reclaim tanks

Recirculatingpump

To restrooms

or laundry, based upon thesoapy nature of the contami-nant. The source was quicklynarrowed down to a car washand the proprietor was ex-tremely cooperative in admit-ting to the problem andexplaining how it had occurred.The circumstances leading upto the incident were as follows:

• On Saturday, February10, 1979, a high pressure pumpbroke down at the car wash.This pump recycled reclaimedwash and rinse water andpumped it to the initialscrubbers of the car wash. Nopotable plumbing connectionis normally made to the carwash’s scrubber system.

• After the pump brokedown, the car wash ownerwas able to continue operationby connecting a 2-inch hosesection temporarily between thepotable supply within the carwash, and the scrubber cyclepiping.

• On Monday, February12, 1979, the owner repairedthe high pressure pump andresumed normal car washoperations. The 2-inch hoseconnection (cross-connection)was not removed!

• Because of the cross-connection, the newly repairedhigh pressure pump promptlypumped a large quantity ofthe reclaimed wash/rinse waterout of the car wash and into a12-inch water main in thestreet. This in turn was deliv-ered to the many residencesand commercial establishmentsconnected to the water main.

Within 24 hours of theincident, the owner of the carwash had installed a 2-inchreduced pressure principlebackflow preventer on hiswater service and all car washestablishments in Seattle thatused a wash water reclaimsystem were notified of thestate requirement for backflowprevention.

ShipyardBackflowContamination

The cause of the problemwas a direct cross-connectionbetween the on-board saltwater fire protection watersystem and the fresh waterconnected to one of the ships atthe dock. While the shipyardhad been aware of the needfor backflow protection at thedockside tie up area, the devicehad not been delivered andinstalled prior to the time of theincident. As a result, the saltwater on-board fire protectionsystem, being at a greaterpressure than the potablesupply, forced the salt water,through backpressure, into theshipyard potable supply.

Fortunately, a smalldemand for potable water atthe time of the incidentprevented widespread pollutionin the shipyard and the sur-rounding areas.

Water fountains at an EastCoast Shipyard were

posted “No Drinking” asworkers flushed the water linesto eliminate raw river waterthat had entered the shipyardfollowing contamination fromincorrectly connected waterlines between ships at the pierand the shipyard. Some thirdshift employees drank thewater before the pollutionwas discovered and latercomplained of stomach crampsand diarrhea.

CHAPTER TWO • 7

Hexavalentchromiumadded tochilled water

Main plant cooling line

Temperingvalve

Circulatingpumps

Hot waterheater

Lasermachine

Temporarychillerfeed pump

To washrooms

Potab

le wate

r sup

ply

To plant bubblers

To ice making machines

To plant vending machines

Backpressure backflow path

Recommended installation ofbackflow preventer

Chlordane in theWater Main

In October, 1979, approxi-mately three gallons of

chlordane, a highly toxicinsecticide, was sucked back(back-siphoned) into the watersystem of a residential area ofa good sized eastern city.Residents complained that thewater “looked milky, felt greasy,foamed and smelled,” and asone woman put it, “It wassimilar to a combination ofkerosene and Black Flagpesticide.”

The problem developedwhile water departmentpersonnel were repairing awater main. A professionalexterminator, meanwhile, wastreating a nearby home withchlordane for termite elimina-tion. The workman for theexterminator company left one

HexavalentChromium inDrinking Water

In July, 1982, a well meaningmaintenance mechanic, in

attempting to correct a fogginglens in an overcooled lasermachine, installed a temperingvalve in the laser cooling line,and inadvertently set the stagefor a backpressure backflowincident that resulted inhexavalent chromium contami-nating the potable water of alarge electronic manufacturingcompany in Massachusettsemploying 9,000 people.Quantities of 50 parts permillion hexavalent chromiumwere found in the drinkingwater which is sufficient tocause severe vomiting, diarrhea,

end of a garden hose that wasconnected to an outside hosebibb tap in a barrel of dilutedpesticide. During the waterservice interruption, thechlordane solution was back-siphoned from the barrelthrough the house and into thewater mains.

Following numerouscomplaints, the water depart-ment undertook an extensiveprogram of flushing of thewater mains and hand deliveredletters telling residents to flushtheir lines for four hours beforeusing the water. Until the waterlines were clear of the contami-nant, water was hand-hauledinto homes, and people wentout of their homes for showers,meals and every other activityinvolving potable water.Fortunately, due to the obviousbad taste, odor and color of thecontaminated water, no oneconsumed a sufficient quantityto endanger health.

and intestinal sickness.Maintenance crews workingduring the plant shutdownwere able to eliminate the cross-connection and thoroughlyflush the potable water system,thereby preventing a serioushealth hazard from occurring.

The incident occurred asfollows:

• Laser machine lenseswere kept cool by circulatingchilled water that came from alarge refrigeration chiller. Thewater used in the chiller wastreated with hexavalentchromium, a chemical additiveused as an anticorrosive agentand an algicide. As a result, thechilled water presented a toxic,non-potable substance unfit forhuman consumption but very

CHLORDANE

Recommended installation of hose bibbvacuum breaker backflow preventer


Heat exchangerUtilitysink

Sink

Sink

Coffeemachine

Boosterpump

Recommended installationof backflow preventers

Backpressurebackflow

MeterWatermain

Waterfountatin

Roof mounted solar panels

Sink

Chemicalfeeder

acceptable for industrial processwater. No health hazard waspresent as long as the pipingwas identified, kept separatefrom potable drinking waterlines, and not cross-connectedto the potable water supply.

• A maintenancemechanic correctly reasonedthat by adding a temperingvalve to the chilled water line,he could heat up the water a bitand eliminate fogging of thelaser lenses resulting from thechilled water being too cold.The problem with the installa-tion of the tempering valve wasthat a direct cross-connectionhad been inadvertently madebetween the toxic chilled waterand the potable drinking waterline!

• Periodic maintenanceto the chiller system wasperformed in the summer,requiring that an alternatechiller feed pump be tempo-rarily installed. This replace-ment pump had an outletpressure of 150 psi, andpromptly established animbalance of pressure at thetempering valve, thereby over-pressurizing the 60 psi, potablesupply. Backpressure backflowresulted and pushed the toxicchilled water from the waterheater and then into the plant’spotable drinking water supply.Yellowish green water startedpouring out of the drinkingfountains, the washroom, andall potable outlets.

Employee HealthProblems due toCross-Connection

supply line! As the storage tankpressure increased above thesupply pressure, as a result ofthermal expansion, the poten-tial for backpressure backflowwas present. Normally, thiswould not occur because aboost pump in the supply linewould keep the supply pressureto the storage tank alwaysgreater than the highest tankpressure. The addition of rustinhibiting chemicals to thistank greatly increased thedegree of hazard of the liquid.Unfortunately, at the same timethat the fire took place, thepressure in the water mains wasreduced to a dangerously lowpressure and the low pressurecutoff switches simultaneouslyshut off the storage tankbooster pumps. This combina-tion allowed the boiler water,together with its chemicalcontaminants, the opportunityto enter the potable watersupply within the building.When normal pressure wasreestablished in the watermains, the booster pumpskicked in, and the contami-nated water was deliveredthroughout the building.

A cross-connection incidentoccurring in a modern

seven-story office buildinglocated in a large city in NewHampshire, in March, 1980,resulted in numerous cases ofnausea, diarrhea, loss of timeand employee complaints as tothe poor quality of the water.

On Saturday, March 1,1980, a large fire occurred twoblocks away from a seven-storyoffice building in this largeNew Hampshire city. OnSunday, March 2, 1980, themaintenance crew of the officebuilding arrived to perform theweekly cleaning, and afterdrinking the water from thedrinking fountains, andsampling the coffee from thecoffee machines, noticed thatthe water smelled rubbery andhad a strong bitter taste. Uponnotifying the Manchester WaterCompany, water samples weretaken and preliminary analysisdisclosed that the contaminantsfound were not the typicalcontaminants associated withfire line disturbances. Investi-gating teams suspected thateither the nearby fire couldhave siphoned contaminantsfrom adjacent buildings into thewater mains, or the contamina-tion could have been caused bya plumbing deficiency occurringwithin the seven story buildingitself.

Water ph levels of thebuilding water indicated thatan injection of chemicals hadprobably taken place within theseven-story building. Tracing ofthe water lines within thebuilding pinpointed a 10,000gallon hot-water storage tankthat was used for heat storagein the solar heating system. Itdid not have any backflowprotection on the make-up

CHAPTER TWO • 9

Operating room

Air conditioning units

Glycol/waterpressurizedholding tank

Submerged inletcross-connection

Dialysis roomRecommneded installation

of backflow preventer SlightlyopenmanualvalveDialysis

filtrationunit

Intensive careRestroom

Autopsy

Washroom

Laundry facility

Backpressure backflow

Main watersupply

Recommended installationof backflow preventer

Boilerroom

Dialysis MachineContamination

potable supply line and fedthrough a manually operatedcontrol valve. With this valveopen, or partially open, potablemake-up water flowed slowlyinto the glycol/water mixture inthe holding tank until it filledto the point where the pressurein the closed tank equaled thepressure in the potable watersupply feed line. As long as thepotable feed line pressure was atleast equal to, or greater than,the holding tank pressure, nobackflow could occur. The stagewas set for disaster, however.

It was theorized thatsomeone in the medical centerflushed a toilet or turned on a

faucet, which in turn droppedthe pressure in the potablesupply line to the air condition-ing holding tank. Since themanually operated fill valve waspartially open, this allowed theglycol/water mixture to enterthe medical center potablepipelines and flow into thedialysis equipment. The dialysisfiltration system takes out tracechemicals such as those used inthe city water treatment plant,but the system could nothandle the heavy load ofchemicals that it was suddenlysubjected to.

The effect upon the dialysispatients was dramatic: patientsbecame drowsy, confused andfell unconscious, and werepromptly removed to intensivecare where blood samples weretaken. The blood samplesrevealed a build-up of acid andthe medical director stated that,“Something has happened indialysis.” Dialysis was repeatedon the patients a second andthird time.

Tests of the water supply tothe filtration system quicklydetermined the presence of “anundesirable chemical in thewater purification system.” Thepartially open fill valve wasthen found that it had permit-ted the glycol water mix todrain from the air conditioningholding tank into the medicalcenter’s potable supply linesand then into the dialysisfiltration system equipment.

Creosote in theWater Mains


Ethylene glycol, an anti-freeze additive to air

conditioning cooling towerwater, inadvertently entered thepotable water supply system ina medical center in Illinois inSeptember, 1982, and two ofsix dialysis patients succumbedas a direct or indirect result ofthe contamination.

The glycol was added tothe air conditioning water, andthe glycol/water mix was storedin a holding tank that was anintegral part of the medicalcenter’s air conditioning coolingsystem. Pressurized make-upwater to the holding tank wassupplied by a medical center

Creosote entered the waterdistribution system of a

southeastern county waterauthority in Georgia, inNovember, 1984, as a result ofcross-connection between a¾-inch hose that was beingused as a priming line betweena fire service connection and thesuction side of a creosote pump.The hose continually suppliedwater to the pump to ensurethe pump was primed at alltimes. However, while repairswere being made to a privatefire hydrant, the creosote back-siphoned into the water mainsand contaminated a section ofthe water distribution system.

Detailed investigation ofthe cause of the incidentdisclosed that the woodpreservative company, as part oftheir operation, pumpedcreosote from collective pits toother parts of their operation.The creosote pump wouldautomatically shut off when thecreosote in the pit was loweredto a predetermined level. Afterthe creosote returned to ahigher level, the pump wouldrestart. This pump would loseits prime quite often prior tothe pit refilling, and to preventthe loss of prime, the woodpreservative company wouldconnect a hose from a ¾-inchhose bibb, located on the fireservice line, to the suction sideof the pump. The hose bibbremained open at all times in aneffort to continuously keep thepump primed.

Repairs were necessary toone of the private fire hydrantson the wood preservativecompany property, necessitatingthe shutting down of one of twoservice lines and removal of thedamaged fire hydrant for repair.Since the hydrant was at asignificantly lower level thanthe creosote pit, the creosoteback-siphoned through a ¾-inch pump priming hoseconnecting the creosote pit tothe fire service line.

After the repairs weremade to the hydrant, and thewater service restored, thecreosote, now in the fire lines,was forced into the main waterdistribution system.

Kool-Aid LacedWith Chlordane

CHAPTER TWO • 11

Street main

Street main

Creosote pump

Creosotecontaminated flow


Private shut-off

Processwater


In August, 1978, a profes-sional exterminator was

treating a church located in asmall town in South Carolina,for termite and pest control.The highly toxic insecticidechlordane was being mixedwith water in small buckets,and garden hoses were leftsubmerged in the buckets whilethe mixing was being accom-plished. At the same time,water department personnelcame by to disconnect theparsonage’s water line from thechurch to install a separatewater meter for the parsonage.In the process, the water wasshut off in the area of thechurch building. Since thechurch was located on a steephill, and as the remaining waterin the lines was used byresidents in the area, the churchwas among the first places toexperience a negative pressure.

The chlordane was quicklysiphoned into the water lineswithin the church and becamemixed with the Kool-Aid beingprepared by women for thevacation bible school. Approxi-mately a dozen children andthree adults experienceddizziness and nausea. Fortu-nately, none required hospital-ization or medical attention.

Recommended installationof hose bibb vacuum breaker backflow preventer

Chapter Three

A cross-connection1 is thelink or channel connecting

a source of pollution with apotable water supply. Thepolluting substance, in mostcases a liquid, tends to enter thepotable supply if the net forceacting upon the liquid acts inthe direction of the potablesupply. Two factors are thereforeessential for backflow. First,there must be a link betweenthe two systems. Second, theresultant force must be towardthe potable supply.

An understanding of theprinciples of backflow andbacksiphonage requires anunderstanding of the termsfrequently used in theirdiscussion. Force, unless com-pletely resisted, will producemotion. Weight is a type offorce resulting from the earth’sgravitational attraction.Pressure (P) is a force-per-unitarea, such as pounds per squareinch (psi). Atmospheric pressure isthe pressure exerted by theweight of the atmosphere abovethe earth.

Pressure may be referred tousing an absolute scale, poundsper square inch absolute (psia),or gage scale, pounds persquare inch gage (psig).Absolute pressure and gagepressure are related. Absolutepressure is equal to the gagepressure plus the atmosphericpressure. At sea level theatmospheric pressure is 14.7psia. Thus,

Pabsolute = Pgage + 14.7psior

Pgage = Pabsolute – 14.7 psiIn essence then, absolute

pressure is the total pressure.Gage pressure is simply thepressure read on a gage. If thereis no pressure on the gage otherthan atmospheric, the gagewould read zero. Then theabsolute pressure would beequal to 14.7 psi which is theatmospheric pressure.

The term vacuum indicatesthat the absolute pressure is lessthan the atmospheric pressureand that the gage pressure isnegative. A complete or totalvacuum would mean a pressureof 0 psia or -14.7 psig. Since itis impossible to produce a totalvacuum, the term vacuum, asused in the text, will mean alldegrees of partial vacuum. In apartial vacuum, the pressurewould range from slightly lessthan 14.7 psia (0 psig) toslightly greater than 0 psia(-14.7 psig).

Backsiphonage1 results influid flow in an undesirable orreverse direction. It is caused byatmospheric pressure exerted ona pollutant liquid forcing ittoward a potable water supplysystem that is under a vacuum.Backflow, although literallymeaning any type of reversedflow, refers to the flow producedby the differential pressureexisting between two systemsboth of which are at pressuresgreater than atmospheric.

Water Pressure

For an understanding of thenature of pressure and itsrelationship to water depth,consider the pressure exerted onthe base of a cubic foot of waterat sea level. (See Fig. 1) Theaverage weight of a cubic footof water is 62.4 pounds persquare foot gage. The base maybe subdivided into 144-squareinches with each subdivisionbeing subjected to a pressure of0.433 psig.

Suppose another cubic footof water were placed directlyon top of the first (See Fig. 2).The pressure on the top surfaceof the first cube which wasoriginally atmospheric, or0 psig, would now be 0.433psig as a result of the super-imposed cubic foot of water.The pressure of the base ofthe first cube would also beincreased by the same amountof 0.866 psig, or two times theoriginal pressure.

Theory of Backflowand Backsiphonage

62.4#/ft3

0.433 psig

Sea l

evel

12"

12"12"

FIGURE 1.Pressure exerted by 1 foot ofwater at sea level.

1See formal definition in the glossary ofthe appendix


If this process wererepeated with a third cubic footof water, the pressures at thebase of each cube would be1,299 psig, 0.866 psig, and0.433 psig, respectively. It isevident that pressure varieswith depth below a free watersurface; in general each foot ofelevation change, within aliquid, changes the pressure byan amount equal to the weight-per-unit area of 1 foot of theliquid. The rate of increase forwater is 0.433 psi per foot ofdepth.

Frequently water pressureis referred to using the terms“pressure head” or just “head,”and is expressed in units of feetof water. One foot of headwould be equivalent to thepressure produced at the baseof a column of water 1 foot indepth. One foot of head or1 foot of water is equal to 0.433psig. One hundred feet of headis equal to 43.3 psig.

Siphon Theory

Figure 3 depicts the atmo-spheric pressure on a watersurface at sea level. An opentube is inserted vertically intothe water; atmospheric pres-sure, which is 14.7 psia, actsequally on the surface of thewater within the tube and onthe outside of the tube.

level exactly balances theweight of a column of water33.9 feet in height. Theabsolute pressure within thecolumn of water in Figure 4 ata height of 11.5 feet is equal to9.7 psia. This is a partialvacuum with an equivalentgage pressure of -5.0 psig.

As a practical example,assume the water pressure at aclosed faucet on the top of a100-foot high building to be 20psig; the pressure on theground floor would then be63.3 psig. If the pressure at theground were to drop suddenlydue to a heavy fire demand inthe area to 33.3 psig, thepressure at the top would bereduced to -10 psig. If thebuilding water system wereairtight, the water wouldremain at the level of the faucet

because of the partial vacuumcreated by the drop in pressure.If the faucet were opened,however, the vacuum would bebroken and the water levelwould drop to a height of 77feet above the ground. Thus,the atmosphere was supportinga column of water 23 feet high.

Figure 5 is a diagram of aninverted U-tube that has beenfilled with water and placed intwo open containers at sea level.

If the open containers areplaced so that the liquid levelsin each container are at thesame height, a static state willexist; and the pressure at anyspecified level in either leg ofthe U-tube will be the same.

The equilibrium conditionis altered by raising one of thecontainers so that the liquidlevel in one container is 5 feet

If, as shown in Figure 4,the tube is slightly capped anda vacuum pump is used toevacuate all the air from thesealed tube, a vacuum with apressure of 0 psia is createdwithin the tube. Because thepressure at any point in a staticfluid is dependent upon theheight of that point above areference line, such as sea level,it follows that the pressurewithin the tube at sea levelmust still be 14.7 psia. This isequivalent to the pressure at thebase of a column of water 33.9feet high and with the columnopen at the base, water wouldrise to fill the column to a depthof 33.9 feet. In other words, theweight of the atmosphere at sea

0.433 psig24"

0.866 psig Sea

Leve

l

14.7psia14.7 psia

sea level

FIGURE 2.Pressure exerted by 2 feet ofwater at sea level.

FIGURE 3.Pressure on the free surface of aliquid at sea level.

FIGURE 4.Effect of evacuating air from acolumn.

FIGURE 5.Pressure relationships in acontinuous fluid system at thesame elevation.


14.7psia

9.7psia

14.7 psia or0.0 psig

or -5.0 psig

0.0psia

or-14.7psig

Vacuum pump

“Zero” AbsolutePressure

Sea level

39.9

'11

.5'

14.7psia

14.7psia

4.7 psia

10.3 psia 23'

10'

CHAPTER THREE • 13

above the level of the other. (SeeFig. 6.) Since both containersare open to the atmosphere, thepressure on the liquid surfacesin each container will remain at14.7 psia.

If it is assumed that a staticstate exists, momentarily,within the system shown inFigure 6, the pressure in the lefttube at any height above thefree surface in the left containercan be calculated. The pressureat the corresponding level in theright tube above the free surfacein the right container may alsobe calculated.

As shown in Figure 6, thepressure at all levels in the lefttube would be less than atcorresponding levels in the righttube. In this case, a staticcondition cannot exist becausefluid will flow from the higherpressure to the lower pressure;the flow would be from theright tank to the left tank. Thisarrangement will be recognizedas a siphon. The crest of asiphon cannot be higher than33.9 feet above the upper liquid

level, since atmosphere cannotsupport a column of watergreater in height than 33.9 feet.

Figure 7 illustrates howthis siphon principle can behazardous in a plumbingsystem. If the supply valve isclosed, the pressure in the linesupplying the faucet is less thanthe pressure in the supply lineto the bathtub. Flow will occur,therefore, through siphonage,from the bathtub to the openfaucet.

shown that as a fluid acceler-ates, as shown in Figure 8, thepressure is reduced. As waterflows through a constrictionsuch as a converging section ofpipe, the velocity of the waterincreases; as a result, thepressure is reduced. Under suchconditions, negative pressuresmay be developed in a pipe.The simple aspirator is basedupon this principle. If thispoint of reduced pressure islinked to a source of pollution,backsiphonage of the pollutantcan occur.

flow from the source of pollu-tion would occur when pressureon the suction side of the pumpis less than pressure of thepollution source; but this isbackflow, which will be discussedbelow.

The preceding discussionhas described some of themeans by which negativepressures may be created andwhich frequently occur toproduce backsiphonage. Inaddition to the negativepressure or reversed forcenecessary to causebacksiphonage and backflow,there must also be the cross-connection or connecting linkbetween the potable watersupply and the source ofpollution. Two basic types ofconnections may be created inpiping systems. These are thesolid pipe with valved connec-tion and the submerged inlet.


14.7psia

14.7psia

10.3 psia

10'

8.2 psia

15'

5'

FIGURE 6.Pressure relationships in acontinuous fluid system atdifferent elevations.

Valve open

Closed supply

Valve open

Submerged inlet

FIGURE 7.Backsiphonage in a plumbingsystem.

The siphon actions citedhave been produced by reducedpressures resulting from adifference in the water levels attwo separated points within acontinuous fluid system.

Reduced pressure may alsobe created within a fluid systemas a result of fluid motion. Oneof the basic principles of fluidmechanics is the principle ofconservation of energy. Basedupon this principle, it may be

+30 psig +30 psig-10 psig

FIGURE 8.Negative pressure created byconstricted flow.

FIGURE 9.Dynamically reduced pipepressures.

Booster pump

To fixtureFrom pollutionsource

+50 psig

-10psig

One of the commonoccurrences of dynamicallyreduced pipe pressures is foundon the suction side of a pump.In many cases similar to the oneillustrated in Figure 9, the linesupplying the booster pump isundersized or does not havesufficient pressure to deliverwater at the rate at which thepump normally operates. Therate of flow in the pipe may beincreased by a further reductionin pressure at the pump intake.This often results in the creationof negative pressure at thepump intake. This often resultsin the creation of negativepressure. This negative pressuremay become low enough insome cases to cause vaporizationof the water in the line. Actu-ally, in the illustration shown,

Figures 10 and 11 illustratesolid connections. This type ofconnection is often installedwhere it is necessary to supplyan auxiliary piping system fromthe potable source. It is a directconnection of one pipe toanother pipe or receptacle.

Solid pipe connections areoften made to continuous orintermittent waste lines whereit is assumed that the flow willbe in one direction only. Anexample of this would be usedcooling water from a waterjacket or condenser as shown inFigure 11. This type of connec-tion is usually detectable butcreating a concern on the part

of the installer about thepossibility of reversed flow isoften more difficult. Uponquestioning, however, manyinstallers will agree that thesolid connection was madebecause the sewer is occasion-ally subjected to backpressure.

Submerged inlets are foundon many common plumbingfixtures and are sometimesnecessary features of the fixturesif they are to function properly.Examples of this type of designare siphon-jet urinals or waterclosets, flushing rim slop sinks,and dental cuspidors. Oldstylebathtubs and lavatories hadsupply inlets below the floodlevel rims, but modern sanitarydesign has minimized oreliminated this hazard in newfixtures. Chemical and indus-trial process vats sometimeshave submerged inlets wherethe water pressure is used as anaid in diffusion, dispersion andagitation of the vat contents.Even though the supply pipemay come from the floor abovethe vat, backsiphonage canoccur as it has been shown thatthe siphon action can raise aliquid such as water almost 34feet. Some submerged inlets

difficult to control are those which are not apparent until a significant change in water level occurs or where a supply may be conveniently extended below the liquid surface by means of a hose or auxiliary piping. A submerged inlet may be created in numerous ways, and its detection in some of these subtle forms may be difficult.

The illustrations included in part B of the appendix are intended to describe typical examples of backsiphonage, showing in each case the nature of the link or cross-connection, and the cause of the negative pressure.

Backflow

Backflow1, as described in this course, refers to reversed flow due to backpressure other than siphonic action. Any intercon-nected fluid systems in which the pressure of one exceeds the pressure of the other may have flow from one to the other as a result of the pressure differen-tial. The flow will occur from the zone of higher pressure to the zone of lower pressure. This type of backflow is of concern in buildings where two or more piping systems are maintained. The potable water supply is usually under pressure directly from the city water main. Occasionally, a booster pump is used. The auxiliary system is often pressurized by a centrifical pump, although backpressure may be caused by gas or steam pressure from a boiler. A

reversal in differential pressuremay occur when pressure in thepotable system drops, for somereason, to a pressure lower thanthat in the system to which thepotable water is connected.

The most positive methodof avoiding this type ofbackflow is the total or com-plete separation of the twosystems. Other methods usedinvolve the installation ofmechanical devices. All meth-ods require routine inspectionand maintenance.

Dual piping systems areoften installed for extra protec-tion in the event of an emer-gency or possible mechanicalfailure of one of the systems.Fire protection systems are anexample. Another example isthe use of dual water connec-tions to boilers. These installa-tions are sometimes inter-connected, thus creating ahealth hazard.

The illustrations in part Cof the appendix depict installa-tions where backflow underpressure can occur, describingthe cross-connection and thecause of the reversed flow.

CHAPTER THREE • 15

FIGURE 11Valved connection betweenpotable water and sanitary sewer.

City supply

Sanitary sewer

Condenser

FIGURE 10.Valved connections betweenpotable water and nonpotablefluid.

Non potable Potable


Chapter Four

A wide choice of devicesexists that can be used to

prevent backsiphonage andbackpressure from addingcontaminated fluids or gasesinto a potable water supplysystem. Generally, the selectionof the proper device to use isbased upon the degree of hazardposed by the cross-connection.Additional considerations arebased upon piping size, location,and the potential need toperiodically test the devices toinsure proper operation.

There are six basic types ofdevices that can be used tocorrect cross-connections: airgaps, barometric loops, vacuumbreakers—both atmosphericand pressure type, double checkwith intermediate atmosphericvent, double check valveassemblies, and reduced pressureprinciple devices. In general, allmanufacturers of these devices,with the exception of thebarometric loop, produce themto one or more of three basicstandards, thus insuring thepublic that dependable devicesare being utilized and marketed.The major standards in theindustry are: American Societyof Sanitary Engineers ASSE),American Water Works Associa-tion (AWWA), and the Univer-sity of California Foundation forCross-Connection Control andHydraulic Research.

Air Gap

Air gaps are non-mechanicalbackflow preventers that arevery effective devices to be usedwhere either backsiphonage orbackpressure conditions mayexist. Their use is as old aspiping and plumbing itself, butonly relatively recently havestandards been issued thatstandardize their design. Ingeneral, the air gap must betwice the supply pipe diameterbut never less than one inch.See Figure 12.

(2) The air gap may be easilydefeated in the event that the“2D” requirement was purposelyor inadvertently compromised.Excessive splash may be encoun-tered in the event that higherthan anticipated pressures orflows occur. The splash may be acosmetic or true potentialhazard—the simple solutionbeing to reduce the “2D”dimension by thrusting thesupply pipe into the receivingfunnel. By so doing, the air gapis defeated.(3) At an air gap, we expose thewater to the surrounding airwith its inherent bacteria, dustparticles, and other airbornepollutants or contaminants. Inaddition, the aspiration effect ofthe flowing water can drag downsurrounding pollutants into thereservoir or holding tank.(4) Free chlorine can come out oftreated water as a result of the airgap and the resulting splash andchurning effect as the waterenters the holding tanks. Thisreduces the ability of the waterto withstand bacteria contamina-tion during long term storage.(5) For the above reasons, airgaps must be inspected asfrequently as mechanicalbackflow preventers. They arenot exempt from an in-depthcross-connection control pro-gram requiring periodic inspec-tion of all backflow devices.

Air gaps may be fabricatedfrom commercially availableplumbing components orpurchased as separate units andintegrated into plumbing andpiping systems. An example ofthe use of an air gap is shown inFigure 13.


Methods and Devicesfor the Prevention ofBackflow andBack-Siphonage

An air gap, although anextremely effective backflowpreventer when used to preventbacksiphonage and backpres-sure conditions, does interruptthe piping flow with corre-sponding loss of pressure forsubsequent use. Consequently,air gaps are primarily used atend of the line service wherereservoirs or storage tanks aredesired. When contemplatingthe use of an air gap, someother considerations are:(1) In a continuous pipingsystem, each air gap requiresthe added expense of reservoirsand secondary pumpingsystems.

FIGURE 12.Air gap.

Diameter“D”

“2D”

Barometric Loop

The barometric loop consists ofa continuous section of supplypiping that abruptly rises to aheight of approximately 35 feetand then returns back down tothe originating level. It is a loopin the piping system thateffectively protects againstbacksiphonage. It may not beused to protect against back-pressure.

Its operation, in theprotection against back-siphonage, is based upon theprinciple that a water column,at sea level pressure, will notrise above 33.9 feet (Ref.Chapter 3, Fig. 4 Page 13).

In general, barometricloops are locally fabricated, andare 35 feet high.

Atmospheric VacuumBreaker

These devices are among thesimplest and least expensivemechanical types of backflowpreventers and, when installedproperly, can provide excellentprotection against back-siphonage. They must not beutilized to protect againstbackpressure conditions.Construction consists usually ofa polyethylene float which isfree to travel on a shaft and sealin the uppermost positionagainst atmosphere with anelastomeric disc. Water flowlifts the float, which then causesthe disc to seal. Water pressurekeeps the float in the upwardsealed position. Termination ofthe water supply will cause thedisc to drop down venting theunit to atmosphere and therebyopening downstream piping toatmospheric pressure, thuspreventing backsiphonage.Figure 15 shows a typicalatmospheric breaker.

In general, these devicesare available in ½-inch through3-inch size and must beinstalled vertically, must nothave shutoffs downstream,and must be installed at least6-inches higher than the finaloutlet. They cannot be testedonce they are installed in theplumbing system, but are, forthe most part, dependable,trouble-free devices forbacksiphonage protection.

Figure 16 shows thegenerally accepted installationrequirements—note that noshutoff valve is downstreamof the device that wouldotherwise keep the atmosphericvacuum breaker under constantpressure.

Figure 17 shows a typicalinstallation of an atmosphericvacuum breaker in a plumbingsupply system.

CHAPTER FOUR • 17

FIGURE 13.Air gap in a piping system.

Supply piping

Tank or reservoir

FIGURE 14.Barometric loop.

FIGURE 15.Atmospheric vacuum breaker.

35'

FIGURE 16.Atmospheric vacuum breakertypical installation.

FIGURE 17.Atmospheric vacuum breaker inplumbing supply system.

Flow condition

Seal

Non flow condition

Not less than 6"

Hose BibbVacuum Breakers

These small devices are aspecialized application of theatmospheric vacuum breaker.They are generally attached tosill cocks and in turn areconnected to hose suppliedoutlets such as garden hoses,slop sink hoses, spray outlets,etc. They consist of a springloaded check valve that sealsagainst an atmospheric outletwhen water supply pressure isturned on. Typical constructionis shown in Figure 18.

When the water supply isturned off, the device vents toatmosphere, thus protectingagainst backsiphonage condi-tions. They should not be usedas backpressure devices. Manualdrain options are available,together with tamper-proofversions. A typical installation isshown in Figure 19.

PressureVacuum Breakers

This device is an outgrowth ofthe atmospheric vacuumbreaker and evolved in responseto a need to have an atmospher-ic vacuum breaker that could beutilized under constant pressureand that could be tested in line.A spring on top of the disc andfloat assembly, two added gatevalves, test cocks, and anadditional first check, providedthe answer to achieve thisdevice. See Figure 20.

These units are available inthe general configurations asshown in Figure 20 in sizes½-inch through 10-inch andhave broad usage in theagriculture and irrigationmarket. Typical agricultural and

industrial applications areshown in Figure 21.

Again, these devices maybe used under constant pressurebut do not protect againstbackpressure conditions. As aresult, installation must be atleast 6- to 12-inches higherthan the existing outlet.

A spill resistant pressurevacuum breaker (SVB) isavailable that is a modificationto the standard pressurevacuum breaker but specificallydesigned to minimize waterspillage. Installation andhydraulic requirements aresimilar to the standard pressurevacuum breaker and thedevices are recommended forinternal use.


Hose bibb vacuum breaker

¾ inch thru 2 inches

2½ inches thru 10 inches

Spring

Gate Valve

Gate Valve

Test cock

Test cock

First check valve

FIGURE 18.Hose bibb vacuum breaker.

FIGURE 19.Typical installation of hose bibbvacuum breaker.

FIGURE 20.Pressure vacuum breaker

Double Check withIntermediateAtmospheric Vent

The need to provide a compactdevice in ½-inch and ¾-inchpipe sizes that protects againstmoderate hazards, is capable ofbeing used under constantpressure and that protectsagainst backpressure, resultedin this unique backflowpreventer. Construction isbasically a double check valvehaving an atmospheric ventlocated between the two checks(See Figure 22).

Line pressure keeps thevent closed, but zero supplypressure or backsiphonage willopen the inner chamber toatmosphere. With this device,extra protection is obtainedthrough the atmospheric ventcapability. Figure 23 shows atypical use of the device on aresidential boiler supply line.

Double Check Valve

A double check valve isessentially two single checkvalves coupled within one bodyand furnished with test cocksand two tightly closing gatevalves (See Figure 24).

The test capability featuregives this device a big advan-tage over the use of twoindependent check valves inthat it can be readily tested todetermine if either or bothcheck valves are inoperativeor fouled by debris. Each checkis spring loaded closed andrequires approximately a poundof pressure to open.

This spring loadingprovides the ability to “bite”through small debris and stillseal—a protection feature notprevalent in unloaded swingcheck valves. Figure 24 shows across section of double checkvalve complete with test cocks.Double checks are commonlyused to protect against low tomedium hazard installationssuch as food processing steamkettles and apartment projects.They may be used undercontinuous pressure and protectagainst both backsiphonage andbackpressure conditions.

CHAPTER FOUR • 19

Vent

2nd check1st check

Drain

Air gap

Automatic feed valveSupply

Return

Boiler

FIGURE 21.Typical agricultural andindustrial application ofpressure vacuum breaker.

FIGURE 22.Double check valve withatmospheric vent.

FIGURE 23.Typical residential use of doublecheck with atmospheric vent.

FIGURE 24.Double check valve.

At least 6"Process tanks

12" minimum abovethe highest outlet

Hose bibb

Double Check DetectorCheck

This device is an outgrowth ofthe double check valve and isprimarily utilized in fire lineinstallations. Its purpose is toprotect the potable supply linefrom possible contamination orpollution from fire line chemicaladditives, booster pump fireline backpressure, stagnant“black water” that sits in firelines over extended periods oftime, the addition of “raw”water through outside firepumper connections (Siameseoutlets), and the detection ofany water movement in the fireline water due to fire lineleakage or deliberate watertheft. It consists of two, springloaded check valves, a bypassassembly with water meter anddouble check valve, and twotightly closing gate valves. SeeFigure 25. The addition of testcocks makes the device testable

to insure proper operation ofboth the primary checks andthe bypass check valve. In theevent of very low fire line waterusage, (theft of water) the lowpressure drop inherent in thebypass system permits the lowflow of water to be meteredthrough the bypass system. In ahigh flow demand, associatedwith deluge fire capability, themain check valves open,permitting high volume, lowrestricted flow, through the twolarge spring loaded checkvalves.

Residential Dual Check

The need to furnish reliable andinexpensive backsiphonage andbackpressure protection forindividual residences resulted inthe debut of the residential dualcheck. Protection of the mainpotable supply from householdhazards such as home photo-graph chemicals, toxic insectand garden sprays, termitecontrol pesticides used byexterminators, etc., reinforced,a true need for such a device.Figure 26 shows a cutaway ofthe device.

It is sized for ½-, ¾-, and1-inch service lines and isinstalled immediately down-stream of the water meter. Theuse of plastic check modulesand elimination of test cocksand gate valves keeps the costreasonable while providinggood, dependable protection.Typical installations are shownin Figures 27 and 28.


Residentialdual check

Water meter

Water meter

1¼" meter thread female inlet with1" NPT thread female union outlet

FIGURE 25.Double check detector check.

FIGURE 26.Residential dual check.

FIGURE 27.Residential installation.

FIGURE 28.Copper horn.

100 psi 95 psi

Out 47 psi

50 psi

Supply 60 psi

94 psi

Reduced PressurePrinciple BackflowPreventer

Maximum protection isachieved against backsiphonageand backpressure conditionsutilizing reduced pressureprinciple backflow preventers.These devices are essentiallymodified double check valveswith an atmospheric ventcapability placed between thetwo checks and designed suchthat this “zone” between thetwo checks is always kept atleast two pounds less than thesupply pressure. With thisdesign criteria, the reducedpressure principle backflowpreventer can provide protec-tion against backsiphonage andbackpressure when both thefirst and second checks becomefouled. They can be used underconstant pressure and at highhazard installations. They arefurnished with test cocks andgate valves to enable testingand are available in sizes ¾-inchthrough 10 inch.

Figure 29A shows typicaldevices representative of ¾-inchthrough 2-inch size and Figure29B shows typical devicesrepresentative of 2½-inchthrough 10-inch sizes.

CHAPTER FOUR • 21

FIGURE 29A.Reduced pressure zone backflowpreventer (¾-inch thru 2-inches).

FIGURE 29B.Reduced pressure zone backflowpreventer (2½-inches thru 10-inches).

Relief valve (rotated 90˚ for clarity)

Reduced pressure zone1st check valve 2nd check valve

94 psi 93 psi100 psi


The principles of operationof a reduced pressure principlebackflow preventer are asfollows:

Flow from the left entersthe central chamber against thepressure exerted by the loadedcheck valve 1. The supplypressure is reduced thereuponby a predetermined amount.The pressure in the centralchamber is maintained lowerthan the incoming supplypressure through the operationof the relief valve 3, whichdischarges to the atmospherewhenever the central chamberpressure approaches within afew pounds of the inlet pres-sure. Check valve 2 is lightlyloaded to open with a pressuredrop of 1 psi in the direction offlow and is independent of thepressure required to open therelief valve. In the event that

the pressure increases down-stream from the device, tendingto reverse the direction of flow,check valve 2 closes, preventingbackflow. Because all valvesmay leak as a result of wear orobstruction, the protectionprovided by the check valves isnot considered sufficient. Ifsome obstruction preventscheck valve 2 from closingtightly, the leakage back intothe central chamber wouldincrease the pressure in thiszone, the relief valve wouldopen, and flow would bedischarged to the atmosphere.

When the supply pressuredrops to the minimum differen-tial required to operate therelief valve, the pressure in thecentral chamber should beatmospheric. If the inletpressure should become lessthan atmospheric pressure,

relief valve 3 should remainfully open to the atmosphere todischarge any water which maybe caused to backflow as aresult of backpressure andleakage of check valve 2.

Malfunctioning of one orboth of the check valves or reliefvalve should always be indi-cated by a discharge of waterfrom the relief port. Under nocircumstances should pluggingof the relief port be permittedbecause the device dependsupon an open port for safeoperation. The pressure lossthrough the device may beexpected to average between10 and 20 psi within thenormal range of operation,depending upon the size andflow rate of the device.

Reduced pressure principlebackflow preventers arecommonly installed on high

hazard installations such asplating plants, where theywould protect against primarilybacksiphonage potential, carwashes where they wouldprotect against backpressureconditions, and funeral parlors,hospital autopsy rooms, etc.The reduced pressure principlebackflow preventer forms thebackbone of cross-connectioncontrol programs. Since it isutilized to protect against highhazard installations, and sincehigh hazard installations are thefirst consideration in protectingpublic health and safety, thesedevices are installed in largequantities over a broad range ofplumbing and water worksinstallations. Figures 31 and 32show typical installations ofthese devices on high hazardinstallations.

Directionof flow

1 2

3

Reversed direction of flow

Reduced pressure principle backflow preventerWater main

Meter

Main

Reduced pressure principlebackflow preventer

FIGURE 30.Reduced pressure zone backflowpreventer — principle of operation.

FIGURE 31.Plating plant installation.

FIGURE 32.Car wash installation.

CHAPTER ONE • 23

FIGURE 33.Typical bypass configurationreduced pressure principledevices

FIGURE 34.Typical installation reducedpressure principle devicehorizontal illustration.

Typical fire line installation doublecheck valve vertical installation.

FIGURE 35.Typical installation reducedpressure principle device verticalillustration.

Reduced pressureprinciple device

Water meter

Note: Device to be set 12" minimum from wall.

Air gap

Drain 12" min. 30" max.


Water meter

Air gap

Elbow

Drain

Note: (1) Refer to manufacturers installation data for vertical mount.(2) Unit to be set at a height to permit ready access for testing and service.(3) Vertical installation only to be used if horizontal installation cannot be achieved.

Reduced pressure principle device

Note: Devices to be set a min. of 12" and a max. of 30" from the floor and 12" from any wall.


Air gap

Drain

Air gap

Drain

Double checkvalve

Alarm check

Grade

OS&Y gate valve

Fire pipe

Siamesecheck

Siamesefitting


FIGURE 36.Typical installation double checkvalve horizontal and verticalinstallation.

FIGURE 37.Typical installation residential dualcheck with straight set andcopperhorn.

Note: Vertical installation only to be used if horizontal installation cannot be achieved.

Double check valve

Double check valve

(unit to be set at a heightthat permits ready accessfor testing and service)

Water meter

Copperhorn with water meter

12" min. 30" max.

Residential dualcheck valve

Residentialdual check

¾" ball valve

¾" ball valve

¾" K-copper

Water meter

Copperhorn with water meter

Chapter Five

Prior to initiating a test ofany backflow device, it is

recommended that the follow-ing procedures be followed:

1. Permission be obtained fromthe owner, or his representative,to shut down the water supply.This is necessary to insure thatsince all testing is accomplishedunder no-flow conditions, theowner is aware that his watersupply will be temporarily shutoff while the testing is beingperformed. Some commercialand industrial operationsrequire constant and uninter-rupted water supplies forcooling, boiler feed, seal pumpwater, etc. and water serviceinterruption cannot be tolerat-ed. The water supply tohospitals and continuousprocess industries cannot beshut off without planned andcoordinated shut downs. Therequest to shut down the watersupply is therefore a necessaryprerequisite to protect thecustomer as well as limit theliability of the tester.

Concurrent with therequest for permission to shutoff the water, it is advisable topoint out to the owner, or hisrepresentative, that while thewater is shut off during the testperiod, any inadvertent use ofwater within the building willreduce the water pressure tozero. Backsiphonage couldresult if unprotected cross-

connections existed whichwould contaminate the buildingwater supply system. In orderto address this situation, it isrecommended that the ownercaution the inhabitants of thebuilding not to use the wateruntil the backflow test iscompleted and the waterpressure restored. Additionaloptions available to the buildingowner would be the installationof two backflow devices inparallel that would enable aprotected bypass flow aroundthe device to be tested. Also, ifall water outlets are protectedwithin the building with“fixture outlet protection”backflow devices, cross-connections would not create aproblem in the event ofpotential backsiphonageconditions occurring whiledevices are tested, or for anyother reason.2. Determine the type of deviceto be tested i.e., double checkvalve or reduced pressureprinciple device.3. Determine the flow direc-tion. (Reference directional flowarrows or wording provided bythe manufacturer on thedevice.)4. Number the test cocks, bleedthem of potential debris, andassemble appropriate test cockadapters and bushings that maybe required.

5. Shut off the downstream(number 2) shut-off valve. (Ref.Item (1) above.)6. Wait several moments priorto hooking up the test kit hoseswhen testing a reduced pressureprinciple device. If water exitsthe relief valve, in all likelihood,the first check valve is fouledand it is impractical to proceedwith the testing until the valveis serviced. This waiting periodis not necessary when testingdouble check valves.7. Hook up the test kit hoses inthe manner appropriate to thedevice being tested and thespecific test being performed.

Test personnel are cau-tioned to be aware and followlocal municipal, county, andstate testing requirements andguidelines as may be dictatedby local authority. The follow-ing test procedures are guide-lines for standard, generallyacceptable test proceduresbut may be amended, superced-ed, or modified by localjurisdiction.

CHAPTER FIVE • 25

Testing Proceduresfor BackflowPreventers

Test Equipment

number 1 shut-off valveopen) bleed test cocksnumber 1 and number 2.

2. Hook up the high pressurehose to number 1 test cockand the low pressure hoseto number 2 test cock.

3. Bleed the high pressurehose, and low pressurehose, in that order, andclose the test kit needlevalves slowly.

4. Record the differentialpressure on the gauge. Areading of 1 psid isacceptable to insure a tightcheck valve.

Test 2 Test the air inlet valvefor a breakaway of 1 psi.1. Connect the high pressure

hose to test cock number 2,and bleed the high pressurehose.

2. Shut off number 1 shut-offvalve.

3. Slowly open the bleed valveof the test kit, and observeand record the psi whenthe air inlet poppet opens.This should be a minimumof 1 psi. Restore the valveto normal service.

Method 2Using a water column sighttube and 90 degree elbowfitting with bleed needleTest 1 Test the internal checkvalve for tightness of 1 psid inthe direction of flow.1. Assemble sight tube to test

cock number 1. Open testcock and fill the tube to aminimum of 36-inches ofwater height.

2. Close number 1 shut-offvalve.

3. Open test cock number 2.The air inlet valve shouldopen and discharge waterthrough number 2 testcock.

4. Open number 1 test cock.The sight tube level ofwater should drop slowlyuntil it stabilizes. Thispoint should be a mini-mum of 28-inches of watercolumn which equals 1 psi.

Test 2 Test the air inlet valvefor a breakaway of 1 psi.1. Assemble sight tube to

test cock number 2. Opentest cock number 2 and fillthe tube to a minimum of36-inches of water height.


3. Bleed water slowly fromthe number 2 test cockbleed needle and observethe water column height asit drops.

4. At the point when the airinlet valve pops open,record the height of thewater column. This pointshould be a minimum of28-inches of water columnwhich equals 1psi.

Restore the valve to normalservice.

Reduced PressurePrinciple BackflowPreventer(Figure 39)Field testing of a reducedpressure principle backflowpreventer is accomplishedutilizing a differential pressuregauge. The device is tested forthree optional characteristics:i.e., (1) the first check valve istight and maintains a minimumof 5 psi differential pressure,(2) the second check valve istight against backpressure and(3) the relief valve opens at aminimum of 2 psi below inletsupply pressure. Testing isperformed as follows:Step 1 Test to insure that thefirst check valve is tight andmaintains a minimum pressureof 5 psi differential pressure.1. Verify that number 1 shut-

off valve is open. Closenumber 2 shut-off valve.If there is no drainagefrom the relief valve it isassumed that the firstcheck is tight.

2. Close all test kit valves.3. Connect the high pressure

hose to test cock number 2.4. Connect the low pressure

hose to test cock number 3.5. Open test cocks number 2

and number 3.6. Open high side bleed

needle valve on test kitbleeding the air from thehigh hose. Close the highside bleed needle valve.

7. Open the low side bleedneedle valve on test kitbleeding air from the lowhose. Close the low sidebleed needle valve. Recordthe differential gaugepressure. It should be aminimum of 5 psid.

For field testing of reducedpressure principle backflow

preventers and double checkvalve assemblies, a differentialpressure test gauge is utilizedhaving a 0 to 15 psi range anda working pressure of 500 psi.Appropriate length of hoseswith necessary fittings accom-pany the test gauge. Severalmanufactured test kits arecommercially available thatincorporate the differentialgauge, hoses, and fittings andare packaged for ease ofportability and come withprotective enclosures or strapsfor hanging. Calibrated watercolumns are commerciallyavailable that are portable andcome with carrying cases.

It is important that all testequipment be periodicallychecked for calibration.

Pressure VacuumBreaker(Figure 38)Field testing of a pressurevacuum breaker involves testingboth the internal spring loadedsoft seated check valve as wellas testing the spring loaded airinlet valve. The testing must beperformed with the devicepressurized and the air inletclosed. The number 2 shut-offvalve must also be closed andthe air inlet valve canopyremoved.

Method 1Using a differential pressuregauge

Test 1 Test the internal checkvalve for tightness of 1 psid inthe direction of flow.1. With the valve body under

pressure, (number 2 shut-off valve closed and

No. 2 shut off valve

Test cockNo. 1

Check valve

Loaded air inlet valve

Air inlet valve canopy

No. 1 shut off valve

Test cockNo. 2

FIGURE 38.


Step 2 Test to insure that thesecond check is tight againstbackpressure. (Figure 40)1. Leaving the hoses hooked

up as in the conclusion ofStep 1 above, connect thebypass hose to test cocknumber 4.

2. Open test cock number 4,the high control needlevalve and the bypass hosecontrol needle valve on thetest kit. (This supplies high

pressure water downstreamof check valve number 2.)If the differential pressuregauge falls off and watercomes out of the reliefvalve, the second check isrecorded as leaking. If thedifferential pressure gaugeremains steady, and nowater comes out of therelief valve, the secondcheck valve is consideredtight

3. To check the tightness ofnumber 2 shut-off valve,leave the hoses hooked upthe same as at the conclu-sion of Step 2 above, andthen close test cocknumber 2. This stops thesupply of any high pressurewater downstream of checkvalve number 2. If thedifferential pressure gaugereading holds steady, thenumber 2 shut-off valve isrecorded as being tight. Ifthe differential pressuregauge drops to zero, thenumber 2 shut-off valve isrecorded as leaking.With a leaking number 2

shut-off valve, the device is, inmost cases, in a flow conditionand the previous readings takenare invalid. Unless a non-flowcondition can be achieved,either through the operation ofan additional shut-off down-stream, or the use of a tempo-rary compensating bypass hose,accurate test results will not beachieved.Step 3 To check that the reliefvalve opens at a minimumpressure of 2 psi below inletpressure.1. With the hoses hooked up

the same as at the conclu-sion of Step #2 (3) above,slowly open up the lowcontrol needle valve on thetest kit and record thedifferential pressure gaugereading at the point whenthe water initially starts todrip from the relief valveopening. This pressurereading should not bebelow 2 psid.

This completes thestandard field test for a reducedpressure principle backflowpreventer. Before removal of thetest equipment, the testershould insure that he opensnumber 2 shut-off valvethereby reestablishing flow.Also, the test kit should bethoroughly drained of all waterto prevent freezing by openingall control needle valves andbleed needle valves.

All test data should berecorded on appropriate forms.(Ref: sample Page 45)

Note: The steps outlined above mayvary in sequence depending upon localregulations and/or preferences.

FIGURE 39.

FIGURE 40.

Temporarybypass hose

Tee

Bleed needle valves

Controlneedlevalves

High sidehose

Low sidehose

Bypass hose

Test c

ock N

o. 1

Test c

ock N

o. 2

Check

valve

No. 1

Test c

ock N

o. 3

Check

valve

No. 2

Test c

ock N

o. 4

No. 1 s

hut o

ff valv

e

No. 2 s

hut o

ff valv

e

CHAPTER FIVE • 27

Double Check ValveAssemblies(Figure 41)Some field test procedures fortesting double check valveassemblies require that thenumber 1 shut-off valve beclosed to accomplish the test.This procedure may introducedebris such as rust and tubercu-lin into the valve that willimpact against check valvenumber 1 or number 2 andcompromise the sealing quality.This potential problem shouldbe considered prior to theselection of the appropriate testmethod.

Two test methods, onerequiring closing of the number1 shut-off valve, and onewithout this requirement arepresented below:

Method 1Utilizing the differentialpressure gauge and notshutting off number 1 shut-offvalve. Figure 41)Step 1 checking check valvenumber 11. Verify that the number 1

shut-off is open. Shut offnumber 2 shut-off valve.

2. Connect the high hose totest cock number 2.

3. Connect the low hose totest cock number 3.

4. Open test cocks 2 and 3.5. Open high side bleed


6. Open low side bleed needlevalve on test kit bleedingthe air from the low hose.Close the low side bleedneedle valve.

7. Record the differentialgauge pressure reading.It should be a minimumof 1 psid.

8. Disconnect the hoses.

Step 2 Checking check valvenumber 2.1. Connect the high hose to

test cock number 3.2. Connect the low hose to

test cock number 4.3. Open test cocks number 3

and 4.4. Open high side bleed



6. Record the differentialgauge pressure reading.It should be a minimumof 1 psid.

7. Disconnect the hoses.

To check tightness ofnumber 2 shut-off valve, boththe check valves must be tightand holding a minimum of1 psid. Also, little or nofluctuation of inlet supplypressure can be tolerated.

The testing is performed asfollows:1. Connect the high hose to

number 2 test cock.2. Connect the low hose to

number 3 test cock.3. Connect the bypass hose to

number 4 test cock.4. Open test cocks numbers

2, 3, and 4.5. Open high side bleed



7. The differential gaugepressure should read aminimum of 1 psid.

8. Open the high side controlneedle valve and the bypasshose control needle valveon the test kit. (Thissupplies high pressurewater downstream of checkvalve number 2).

9. Close test cock number 2.(This stops the supply ofany high pressure waterdownstream of number 2check valve), If thedifferential pressure gaugeholds steady, the number 2shut-off valve is recorded asbeing tight. If the differen-tial pressure gauge drops tozero, the number 2 shut-offvalve is recorded as leaking.


Bleed needle valves

Controlneedlevalves

High side hose Low side hose

Bypass hose

Test c

ock N

o. 1

Test c

ock N

o. 2

Check

valve

No. 1

Test c

ock N

o. 3

Check

valve

No. 2

Test c

ock N

o. 4

No. 1 s

hut o

ff valv

e

No. 2 s

hut o

ff valv

eFIGURE 41.

With a leaking number 2shut-off valve, the device is, inmost cases, in a flow condition,and the previous test readingstaken are invalid. Unless a non-flow condition can be achieved,either through the operation ofan additional shut-off down-stream, or the use of a tempo-rary compensating bypass hose,accurate test results will not beachieved.

This completes thestandard field test for a doublecheck valve assembly. Prior toremoval of the test equipment,the tester should insure that heopens number 2 shut-off valvethereby reestablishing flow. Alltest data should be recorded onappropriate forms and the testkit drained of water.

Method 2Utilizing “Duplex Gauge” orindividual bourdon gauges,requires closing number 1shut-off. (Figure 42)Step 1 checking check valvenumber 11. Connect the high hose to

test cock number 2.2. Connect the low hose to

test cock number 3.3. Open test cocks number 2

and number 3.4. Close number 2 shut-off

valve; then close number 1shut-off valve.

5. By means of the high sideneedle valve, lower thepressure at test cocknumber 2 about 2 psibelow the pressure at testcock number 3. If thissmall difference can bemaintained, then checkvalve number 1 is reportedas “tight”. Proceed to Stepnumber 2. If the smalldifference cannot bemaintained, proceed toStep number 3.

Step 2 checking check valvenumber 2.

Proceed exactly the sametest procedure as in Stepnumber 1, except that thehigh hose is connected to testcock number 3 and the lowhose connected to test cocknumber 4.

Step 31. Open shut-off valve

number 1 to repressurizethe assembly.

2. Loosely attach the bypasshose to test cock number 1,and bleed from the gaugethrough the bypass hoseby opening the low sideneedle valve to eliminatetrapped air. Close low sideneedle valve. Tightenbypass hose. Open testcock number 1.


4. By loosening the low sidehose at test cock number 3,lower the pressure in theassembly about 10 psibelow normal lineconditions.

5. Simultaneously open bothneedle valves. If the checkvalve is holding tight thehigh pressure gauge willbegin to drop while thelow pressure gauge willincrease. Close needlevalves. If the gauge showsthat a small (no more than5 psi) backpressure iscreated and held, then thecheck valve is reported astight. If the check valveleaks, a pressure differentialis not maintained as bothgauges tend to equalize ormove back towards eachother, then the check valveis reported as leaking.With both needle valvesopen enough to keep theneedles on the gaugestationary, the amount ofleakage is visible as thedischarge from theupstream needle valve.

CHAPTER FIVE • 29

High side hose

High side hose

Bypass hose Bypass hose

Duplex gaugeIndividual Bourdon gages mounted on a board

Low side hose

Low side hose

Test c

ock N

o. 1

Test c

ock N

o. 2

Check

valve

No. 1

Test c

ock N

o. 3

Check

valve

No. 2

Test c

ock N

o. 4

No. 1 s

hut o

ff valv

e

No. 2 s

hut o

ff valv

eFIGURE 42.

Chapter Six

Administration ofa Cross-ConnectionControl Program

Responsibility

“containment” theory. Thisapproach utilizes a minimum ofbackflow devices and isolatesthe customer from the watermain. It virtually insulates thecustomer from potentiallycontaminating or polluting thepublic water supply system.While it is recognized that“containment” does not protectthe customer within hisbuilding, it does effectivelyremove him from possiblecontamination to the publicwater supply system. If thewater purveyor elects to protecthis customers on a domesticinternal protective basis and/or“fixture outlet protective basis,”then cross-connection controlprotective devices are placed atinternal high hazard locations aswell as at all locations wherecross-connections exist at the“last free-flowing outlet.” Thisapproach entails extensivecross-connective survey work onbehalf of the water superinten-dent as well as constant policingof the plumbing within eachcommercial, industrial andresidential account. In largewater supply systems, fixtureoutlet protection cross-connection control philosophy,in itself, is a virtual impossibilityto achieve and police due to thequantity of systems involved,the complexity of the plumbingsystems inherent in manyindustrial sites, and the fact thatmany plumbing changes aremade within industrial andcommercial establishments thatdo not require the water depart-ment to license or otherwiseendorse or ratify when contem-plated or completed.

In addition, internalplumbing cross-connectioncontrol survey work is generallyforeign to the average water


Under the provisions of theSafe Drinking Water Act of

1974, the Federal Governmenthas established, through theEPA (Environmental ProtectionAgency), national standards ofsafe drinking water. The statesare responsible for the enforce-ment of these standards as wellas the supervision of publicwater supply systems and thesources of drinking water. Thewater purveyor (supplier) is heldresponsible for compliance tothe provisions of the SafeDrinking Water Act, to includea warranty that water qualityprovided by his operation is inconformance with the EPAstandards at the source, and isdelivered to the customerwithout the quality beingcompromised as a result of itsdelivery through the distribu-tion system. As specified in theCode of Federal Regulations(Volume 40, Paragraph 141.2,Section (c)) “Maximum contam-inant level, means the maxi-mum permissible level of acontaminant in water which isdelivered to the free flowingoutlet of the ultimate user of apublic water system, except inthe case of turbidity where themaximum permissible level ismeasured at the point of entryto the distribution system.Contaminants added to thewater under circumstancescontrolled by the user, exceptthose resulting from corrosionof piping and plumbing causedby water quality, are excludedfrom this definition.”

Figure 43 depicts severaloptions that are open to a waterpurveyor when consideringcross-connection protection tocommercial, industrial, andresidential customers. He mayelect to work initially on the

INTERNALPROTECTIONDEVICES

FIXTUREOUTLETPROTECTIVEDEVICES

Air conditioning cooling tower

Reduced pressure zonebackflow preventer

Laboratory faucet doublecheck valve with

intermediate vacuum breaker

Post mixbeveragemachine

Reducedpressure zone

backflowpreventer

Reducedpressure zone

backflowpreventer

Reduced pressurezone backflow

preventer

Double check valvebackflowpreventer

Photodevelopingequipment

Cafeteriacooking

kettleSlop sink

Containment device

Boiler

Dishwasher

Laboratory Sinks

Atmosphericvacuumbreaker

Process tank

Hosevacuum breaker

Backflow preventerwith intermediateatmospheric vent

Reduced pressurezone backflow

preventerDedicated

line

FIGURE 43.

purveyor and is not normally aportion of his job description orduties. While it is admirable forthe water purveyor to acceptand perform survey work, heshould be aware that he runsthe risk of additional liability inan area that may be in conflictwith plumbing inspectors,maintenance personnel andother public health officials.

Even where extensive“fixture outlet protection,”cross-connection controlprograms are in effect throughthe efforts of an aggressive andthorough water supply cross-connection control program,the water authorities should alsohave an active “containment”program in order to address themany plumbing changes thatare made and that are inherentwithin commercial and industri-al establishments. In essence,fixture outlet protectionbecomes an extension beyondthe “containment” program.

Also, in order for thesupplier of water to providemaximum protection of thewater distribution system,consideration should be given torequiring the owner of apremise (commercial, industrial,or residential) to provide at hisown expense, adequate proofthat his internal water systemcomplies with the local or stateplumbing code(s). In addition,he may be required to install,have tested, and maintain, allbackflow protection devices thatwould be required—at his ownexpense!

The supplier of watershould have the right of entryto determine degree of hazardand the existence of cross-connections in order to protectthe potable water system. By sodoing he can assess the overall

nature of the facility and itspotential impact on the watersystem (determine degree ofhazard], personally see actualcross-connections that couldcontaminate the water system,and take appropriate action toinsure the elimination of thecross-connection or the installa-tion of required backflow devices.

To assist the water purvey-or in the total administrationof a cross-connection controlprogram requires that all publichealth officials, plumbinginspectors, building managers,plumbing installers, andmaintenance men participateand share in the responsibilityto protect the public health andsafety of individuals from cross-connections and contaminationor pollution of the public watersupply system.

Dedicated Line

Figure 43 also depicts the useof a “dedicated” potable waterline. This line initiates immedi-ately downstream of the watermeter and is “dedicated” solelyfor human consumption i.e.,drinking fountains, safetyshowers, eye wash stations, etc.It is very important that thispiping be color coded through-out in accordance with localplumbing regulations, flowdirection arrows added, and thepiping religiously policed toinsure that no cross-connectionsto other equipment or pipingare made that could compro-mise water quality. In the eventthat it is felt that policing ofthis line cannot be reliablymaintained or enforced, theinstallation of a containmentdevice on this line should be aconsideration.

Method of Action

(5) Equip the water authoritywith backflow device test kits.(6) Conduct meeting(s) withthe local plumbing inspectionpeople, building inspectors, andlicensed plumbers in the areawho will be active in theinspection, installations andrepair of backflow devices.Inform them of the intent of theprogram and the part that theycan play in the successfulimplementation of the program.(7) Prior to initiating a surveyof the established commercialand industrial installations,prepare a list of these establish-ments from existing records,then prioritize the degree ofhazard that they present to thewater system, i.e., platingplants, hospitals, car washfacilities, industrial metalfinishing and fabrication,mortuaries, etc. These will bethe initial facilities inspected forcross-connections and will befollowed by less hazardousinstallations.(8) Insure that any newconstruction plans are reviewedby the water authority to assessthe degree of hazard and insurethat the proper backflowpreventer is installed concurrentwith the potential degree ofhazard that the facility presents.(9) Establish a residentialbackflow protection program thatwill automatically insure that aresidential dual check backflowdevice is installed automatically atevery new residence.(10) As water meters arerepaired or replaced at residen-ces, insure that a residentialdual check backflow preventeris set with the new or reworkedwater meter. Be sure to havethe owner address thermalexpansion provisions.

CHAPTER SIX • 31

A complete cross-connectioncontrol program requires a

carefully planned and executedinitial action plan followed byaggressive implementation andconstant follow-up. Properstaffing and education ofpersonnel is a requirement toinsure that an effective programis achieved. A recommendedplan of action for a cross-connection control programshould include the followingcharacteristics:(1) Establish a cross-connectioncontrol ordinance at the locallevel and have it approved bythe water commissioners, townmanager, etc., and insure that itis adopted by the town orprivate water authority as alegally enforceable document.(2) Conduct public informativemeetings that define theproposed cross-connectioncontrol program, review thelocal cross-connection controlordinance, and answer allquestions that may ariseconcerning the reason for theprogram, why and how thesurvey will be conducted, andthe potential impact upon theindustrial, commercial andresidential water customers.Have state authorities and thelocal press and radio attend themeeting.(3) Place written notices of thepending cross-connectioncontrol program in the localnewspaper, and have the localradio station make announce-ments about the program as apublic service notice.(4) Send employees who willadminister the program, to acourse, or courses, on backflowtester certification, backflowsurvey courses, backflow devicerepair courses, etc.

(11) Prepare a listing of alltestable backflow devices in thecommunity and insure thatthey are tested by certified testpersonnel at the time intervalsconsistent with the local cross-connection control ordinance.(12) Prepare and submittesting documentation ofbackflow devices to the Stateauthority responsible formonitoring this data.(13) Survey all commercial andindustrial facilities and requireappropriate backflow protectionbased upon the containmentphilosophy and/or internalprotection and fixture outletprotection. Follow up to insurethat the recommended devicesare installed and tested on bothan initial basis and a periodicbasis consistent with the cross-connection control ordinance.

The surveys should beconducted by personnelexperienced in commercial andindustrial processes. The ownersor owners representatives,should be questioned as to whatthe water is being used for inthe facility and what hazardsthe operations may present tothe water system (both withinthe facility and to the waterdistribution system) in theevent that a backsiphonage orbackpressure condition were toexist concurrent with a non-protected cross-connection. Inthe event that experiencedsurvey personnel are notavailable within the waterauthority to conduct the survey,consideration should be givento having a consulting firmperform the survey on behalf ofthe water department.

Cross-ConnectionControl SurveyWork

connection survey will be ofbenefit to him.(3) Ask what processes areinvolved within the facility andfor what purpose potable wateris used, i.e., do the boilers havechemical additives? Are airconditioning cooling towers inuse with chemical additives? Dothey use water savers withchemical additives? Do theyhave a second source of water(raw water from wells, etc.) inaddition to the potable watersupply? Does the process watercross-connect with potentiallyhazardous chemical etchingtanks, etc.?(4) Request “as-built” engineer-ing drawings of the potablewater supply in order to traceout internal potable lines andpotential areas of cross-connections.(5) Initiate the survey bystarting at the potable entrancesupply (the water meter in mostcases) and then proceed withthe internal survey in the eventthat total internal protectivedevices and fixture outletprotective devices are desired.(6) Survey the plant facilitieswith the objective of looking forcross-connections at all potablewater outlets such as:

Hose bibbsSlop sinksWash room facilitiesCafeteria and kitchensFire protection and

Siamese outletsIrrigation outletsBoiler roomsMechanical roomLaundry facilities

(hospitals)Production floor

(7) Make a sketch of all areasrequiring backflow protectiondevices.

(8) Review with the host whatyou have found and explain thefindings to him. Inform himthat he will receive a writtenreport documenting thefindings together with a writtenrecommendation for correctiveaction. Attempt to answer allquestions at this time. Reviewthe findings with the owner ormanager if time and circum-stances permit.(9) Document all findings andrecommendations prior topreparing the written report.Include as many sketches orphotos with the final report aspossible. If the located crossconnection(s) cannot beeliminated, state the generictype of backflow preventerrequired at each cross connec-tion found.(10) Consider requiring orrecommending compliance ofthe survey findings within adefinitive time frame. (ifappropriate authority is ineffect).


Cross-connection controlsurvey work should only

be performed by personnelknowledgeable about commer-cial and industrial potentialcross-connections as well asgeneral industrial uses for bothpotable and process water. If“containment” is the primeobjective of the survey, thenonly sufficient time need bespent in the facility to deter-mine the degree of hazardinherent within the facility oroperation. Once this is deter-mined, a judgment can bemade by the cross-connectioncontrol inspector as to whattype of backflow protectivedevice will be needed at thepotable supply entrance, orimmediately downstream of thewater meter. In the event thatthe cross-connection controlprogram requires “total”protection to the last freeflowing outlet, then the surveymust be conducted in depth tovisually inspect for all cross-connections within the facilityand make recommendationsand requirements for fixtureoutlet protective devices,internal protective devices, andcontainment devices.

It is recommended thatconsideration be given to thefollowing objectives whenperforming a cross-connectioncontrol survey:(1) Determine if the survey willbe conducted with a pre-arranged appointment orunannounced.(2) Upon entry, identifyyourself and the purpose of thevisitation and request to see theplant manager, owner, ormaintenance supervisor in orderto explain the purpose of thevisit and why the cross-

Chapter Seven

The successful promotion ofa cross-connection control

and backflow preventionprogram in a municipalitywill be dependent upon legalauthority to conduct such aprogram. Where a communityhas adopted a modern plumb-ing code, such as the NationalPlumbing Code, ASA A40.8-1955, or subsequent revisionsthereof, provisions of the codewill govern backflow andcross-connections. It thenremains to provide an ordinancethat will establish a programof inspection for an eliminationof cross- and backflow connec-tions within the community.Frequently authority for sucha program may already bepossessed by the water depart-ment or water authority. Insuch cases no further documentmay be needed. A cross-connection control ordinanceshould have at least threebasic parts.

Water Department NameCross-Connection Control Program

I. PurposeA. To protect the public potable water supply served by the

( ) Water Department from the possibility of contaminationor pollution by isolating, within its customers internal distributionsystem, such contaminants or pollutants which could backflow orback-siphon into the public water system.

B. To promote the elimination or control of existing cross-connections, actual or potential, between its customers in-plantpotable water system, and non-potable systems.

C. To provide for the maintenance of a continuing programof cross-connection control which will effectively prevent thecontamination or pollution of all potable water systems by cross-connection.

II. AuthorityA. The Federal Safe Drinking Water Act of 1974, and the

statutes of the State of ( ) Chapters ( ) the waterpurveyor has the primary responsibility for preventing water fromunapproved sources, or any other substances, from entering thepublic potable water system.

B. ( ) Water Department, Rules and Regulations,adopted.

CHAPTER SEVEN • 33

Cross-ConnectionControl and BackflowPrevention Program

1. Authority for establish-ment of a program.

2. Technical provisionsrelating to eliminatingbackflow and cross-connections.

3. Penalty provisions forviolations.The following model

program is suggested formunicipalities who desire toadopt a cross-connectioncontrol ordinance. Communi-ties adopting ordinances shouldcheck with State health officialsto assure conformance withState codes. The form of theordinance should comply withlocal legal requirements andreceive legal adoption from thecommunity.

CROSS CONNECTION CONTROLMODEL PROGRAM

WATER DEPARTMENT NAMEADDRESS

DATE

Approved _________________

Date _____________________

III. ResponsibilityThe Director of Municipal Services shall be responsible for the

protection of the public potable water distribution system fromcontamination or pollution due to the backflow or backsiphonageof contaminants or pollutants through the water service connec-tion. If, in the judgment of the Director of Municipal Services, anapproved backflow device is required at the city’s water serviceconnection to any customer’s promises, the Director, or hisdelegated agent, shall give notice in writing to said customer toinstall an approved backflow prevention device at each serviceconnection to his premises. The customer shall, within 90 daysinstall such approved device, or devices, at his own expense, andfailure or refusal, or inability on the part of the customer to installsaid device or devices within ninety (90) days, shall constitute aground for discontinuing water service to the premises until suchdevice or devices have been properly installed.

IV. Definitions

A. ApprovedAccepted by the Director of Municipal Services as meeting an

applicable specification stated or cited in this regulation, or assuitable for the proposed use.B. Auxiliary Water Supply

Any water supply, on or available, to the premises other thanthe purveyor’s approved public potable water supply.C. Backflow

The flow of water or other liquids, mixtures or substances,under positive or reduced pressure in the distribution pipes of apotable water supply from any source other than its intendedsource.D. Backflow Preventer

D.3 Barometric LoopA fabricated piping arrangement rising at least thirty five (35)

feet at its topmost point above the highest fixture it supplies. It isutilized in water supply systems to protect against backsiphonage.D.4 Double Check Valve Assembly

An assembly of two (2) independently operating spring loadedcheck valves with tightly closing shut off valves on each side of thecheck valves, plus properly located test cocks for the testing of eachcheck valve.D.5 Double Check Valve with Intermediate Atmospheric Vent

A device having two (2) spring loaded check valves separatedby an atmospheric vent chamber.D.6 Hose Bibb Vacuum Breaker

A device which is permanently attached to a hose bibb andwhich acts as an atmospheric vacuum breaker.D.7 Pressure Vacuum Breaker

A device containing one or two independently operated springloaded check valves and an independently operated spring loadedair inlet valve located on the discharge side of the check or checks.Device includes tightly closing shut-off valves on each side of thecheck valves and properly located test cocks for the testing of thecheck valve(s).D.8 Reduced Pressure Principle Backflow Preventer

An assembly consisting of two (2) independently operatingapproved check valves with an automatically operating differentialrelief valve located between the two (2) check valves, tightlyclosing shut-off valves on each side of the check valves plusproperly located test cocks for the testing of the check valves andthe relief valve.D.9 Residential Dual Check

An assembly of two (2) spring loaded, independently operat-ing check valves without tightly closing shut-off valves and testcocks. Generally employed immediately downstream of the watermeter to act as a containment device.E. Backpressure

A condition in which the owners system pressure is greaterthan the suppliers system pressure.F. Backsiphonage

The flow of water or other liquids, mixtures or substances intothe distribution pipes of a potable water supply system from anysource other than its intended source caused by the suddenreduction of pressure in the potable water supply system.G. Commission

The State of ( ) Control Commission.

A device or means designed to prevent backflow orbacksiphonage. Most commonly categorized as air gap, reduced pressure principle device, double check valve assembly, pressure vacuum breaker, atmospheric vacuum breaker, hose bibb vacuum breaker, residential dual check, double check with intermediate atmospheric vent, and barometric loop.D.1 Air Gap

A physical separation sufficient to prevent backflow between the free-flowing discharge end of the potable water system and any other system. Physically defined as a distance equal to twice the diameter of the supply side pipe diameter but never less than one (1) inch.D.2 Atmospheric Vacuum Breaker

A device which prevents backsiphonage by creating an atmospheric vent when there is either a negative pressure or subatmospheric pressure in a water system.


H. ContainmentA method of backflow prevention which requires a backflow

prevention preventer at the water service entrance.I. Contaminant

A substance that will impair the quality of the water to adegree that it creates a serious health hazard to the public leadingto poisoning or the spread of disease.J. Cross-Connection

Any actual or potential connection between the public watersupply and a source of contamination or pollution.K. Department

City of ( ) Water Department.L. Fixture Isolation

A method of backflow prevention in which a backflowpreventer is located to correct a cross connection at an in-plantlocation rather than at a water service entrance.M. Owner

Any person who has legal title to, or license to operate orhabitat in, a property upon which a cross-connection inspection isto be made or upon which a cross-connection is present.N. Person

Any individual, partnership, company, public or privatecorporation, political subdivision or agency of the State Depart-ment, agency or instrumentality or the United States or any otherlegal entity.O. Permit

A document issued by the Department which allows the use ofa backflow preventer.P. Pollutant

A foreign substance, that if permitted to get into the publicwater system, will degrade its quality so as to constitute a moder-ate hazard, or impair the usefulness or quality of the water to adegree which does not create an actual hazard to the public healthbut which does adversely and unreasonably effect such water fordomestic use.Q. Water Service Entrance

That point in the owners water system beyond the sanitarycontrol of the District; generally considered to be the outlet end ofthe water meter and always before any unprotected branch.R. Director of Municipal Services

The Director, or his delegated representative in charge of the( ) Department of Municipal Services, is invested with theauthority and responsibility for the implementation of a cross-connection control program and for the enforcement of theprovisions of the Ordinance.

V. Administration

A. The Department will operate a cross-connection controlprogram, to include the keeping of necessary records, which fulfillsthe requirements of the Commission’s Cross-Connection Regula-tions and is approved by the Commission.B. The Owner shall allow his property to be inspected for possiblecross-connections and shall follow the provisions of theDepartment’s program and the Commission’s Regulations if across-connection is permitted.C. If the Department requires that the public supply be protectedby containment, the Owner shall be responsible for water qualitybeyond the outlet end of the containment device and should utilizefixture outlet protection for that purpose.

He may utilize public health officials, or personnel from theDepartment, or their delegated representatives, to assist him in thesurvey of his facilities and to assist him in the selection of properfixture outlet devices, and the proper installation of these devices.

VI. Requirements

A. Department1. On new installations, the Department will provide on-

site evaluation and/or inspection of plans in order to determinethe type of backflow preventer, if any, that will be required, willissue permit, and perform inspection and testing. In any case, aminimum of a dual check valve will be required in any newconstruction.

2. For premises existing prior to the start of this program,the Department will perform evaluations and inspections of plansand/or premises and inform the owner by letter of any correctiveaction deemed necessary, the method of achieving the correction,and the time allowed for the correction to be made. Ordinarily,ninety (90) days will be allowed, however, this time period may beshortened depending upon the degree of hazard involved and thehistory of the device(s) in question.

3. The Department will not allow any cross-connection toremain unless it is protected by an approved backflow preventer forwhich a permit has been issued and which will be regularly testedto insure satisfactory operation.

4. The Department shall inform the Owner by letter, ofany failure to comply, by the time of the first re-inspection. TheDepartment will allow an additional fifteen (15) days for thecorrection. In the event the Owner fails to comply with thenecessary correction by the time of the second re-inspection, theDepartment will inform the Owner by letter, that the waterservice to the Owner’s premises will be terminated within aperiod not to exceed five (5) days. In the event that the Ownerinforms the Department of extenuating circumstances as to whythe correction has not been made, a time extension may begranted by the Department but in no case will exceed an addi-tional thirty (30) days.


5. If the Department determines at any time that a seriousthreat to the public health exists, the water service will be termi-nated immediately.

6. The Department shall have on file, a list of PrivateContractors who are certified backflow device testers. All chargesfor these tests will be paid by the Owner of the building orproperty.

7. The Department will begin initial premise inspections todetermine the nature of existing or potential hazards, following theapproval of this program by the Commission, during the calendaryear ( ). Initial focus will be on high hazard industries andcommercial premises.B. Owner

1. The Owner shall be responsible for the elimination or

VII.Degree of HazardThe Department recognizes the threat to the public water

system arising from cross-connections. All threats will be classifiedby degree of hazard and will require the installation of approvedreduced pressure principle backflow prevention devices or doublecheck valves.

VIII. PermitsThe Department shall not permit a cross-connection within

the public water supply system unless it is considered necessary andthat it cannot be eliminated.

A. Cross-connection permits that are required for eachbackflow prevention device are obtained from the Department. Afee of ( ) dollars will be charged for the initial permit and( ) dollars for the renewal of each permit.

B. Permits shall be renewed every ( ) years and arenon-transferable. Permits are subject to revocation and becomeimmediately revoked if the Owner should so change the type ofcross-connection or degree of hazard associated with the service.

C. A permit is not required when fixture isolation is achievedwith the utilization of a non-testable backflow preventer.

IX. Existing in-use backflow prevention devices.Any existing backflow preventer shall be allowed by the

Department to continue in service unless the degree of hazard issuch as to supercede the effectiveness of the present backflowpreventer, or result in an unreasonable risk to the public health.Where the degree of hazard has increased, as in the case of aresidential installation converting to a business establishment, anyexisting backflow preventer must be upgraded to a reducedpressure principle device, or a reduced pressure principle devicemust be installed in the event that no backflow device was present.

X. Periodic TestingA. Reduced pressure principle backflow devices shall be

tested and inspected at least semi-annually.B. Periodic testing shall be performed by the Department’s

certified tester or his delegated representative. This testing will bedone at the owner’s expense.

C. The testing shall be conducted during the Department’sregular business hours. Exceptions to this, when at the request ofthe owner, may require additional charges to cover the increasedcosts to the Department.

D. Any backflow preventer which fails during a periodictest will be repaired or replaced. When repairs are necessary,upon completion of the repair the device will be re-tested atowners expense to insure correct operation. High hazard situa-tions will not be allowed to continue unprotected if the backflowpreventer fails the test and cannot be repaired immediately. Inother situations, a compliance date of not more than thirty (30)days after the test date will be established. The owner is respon-

protection of all cross-connections on his premises.2. The Owner, after having been informed by a letter from

the Department, shall at his expense, install, maintain, and test, or have tested, any and all backflow preventers on his premises.

3. The Owner shall correct any malfunction of the backflowpreventer which is revealed by periodic testing.

4. The Owner shall inform the Department of any proposedor modified cross-connections and also any existing cross-connections of which the Owner is aware but has not been found by the Department.

5. The Owner shall not install a bypass around any backflowpreventer unless there is a backflow preventer of the same type on the bypass. Owners who cannot shut down operation for testing of the device(s) must supply additional devices necessary to allow testing to take place. (Ref. Fig. 33 page 23.)

6. The Owner shall install backflow preventers in a mannerapproved by the Department. (Ref. Figures 3 through 37, pages 23 through 24.)

7. The Owner shall install only backflow preventers ap-proved by the Department or the Commission.

8. Any Owner having a private well or other private watersource, must have a permit if the well or source is cross-connected to the Department’s system. Permission to cross-connect may be denied by the Department. The Owner may be required to install a backflow preventer at the service entrance if a private water source is maintained, even if it is not cross-connected to the Department’s system.

9. In the event the Owner installs plumbing to providepotable water for domestic purposes which is on the Department’s side of the backflow preventer, such plumbing must have its own backflow preventer installed.

10. The Owner shall be responsible for the payment of all feesfor permits, annual or semi-annual device testing, retesting in the case that the device fails to operate correctly, and second re-inspections for non-compliance with Department or Commission requirements.


sible for spare parts, repair tools, or a replacement device. Parallelinstallation of two (2) devices is an effective means of the ownerinsuring that uninterrupted water service during testing or repairof devices and is strongly recommended when the owner desiressuch continuity. (Ref. Fig. 33 page 23.)

E. Backflow prevention devices will be tested more fre-quently than specified in A. above, in cases where there is a historyof test failures and the Department feels that due to the degree ofhazard involved, additional testing is warranted. Cost of theadditional tests will be born by the owner.

XI. Records and Reports

A. RecordsThe Department will initiate and maintain the following:1. Master files on customer cross-connection tests and/or

inspections.2. Master files on cross-connection permits.3. Copies of permits and permit applications.4. Copies of lists and summaries supplied to the

Commission.B. Reports

The Department will submit the following to the Commission.1. Initial listing of low hazard cross-connections to the State.2. Initial listing of high hazard cross-connections to the

State.3. Annual update lists of items 1 and 2 above.4. Annual summary of cross-connection inspections to the

State.

XII. Fees and ChargesThe Department will publish a list of fees or charges for the

following services or permits:1. Testing fees2. Re-testing fees3. Fee for re-inspection4. Charges for after-hours inspections or tests.

Addendum

1. Residential dual checkEffective the date of the acceptance of this Cross-Connection

Control Program for the Town of ( ) all new residentialbuildings will be required to install a residential dual check deviceimmediately downstream of the water meter. (Ref. Figure 37page 24.) Installation of this residential dual check device on aretrofit basis on existing service lines will be instituted at a timeand at a potential cost to the homeowner as deemed necessary bythe Department.

The owner must be aware that installation of a residential dualcheck valve results in a potential closed plumbing system withinhis residence. As such, provisions may have to be made by theowner to provide for thermal expansion within his closed loopsystem, i.e., the installation of thermal expansion devices and/orpressure relief valves.

2. StrainersThe Department strongly recommends that all new retrofit

installations of reduced pressure principle devices and double checkvalve backflow preventers include the installation of strainerslocated immediately upstream of the backflow device. The installa-tion of strainers will preclude the fouling of backflow devices due toboth foreseen and unforeseen circumstances occurring to the watersupply system such as water main repairs, water main breaks, fires,periodic cleaning and flushing of mains, etc. These occurrencesmay “stir up” debris within the water main that will cause foulingof backflow devices installed without the benefit of strainers.


Appendix A

Partial List ofPlumbing HazardsFixtures with DirectConnections

Description

Air conditioning, air washerAir conditioning, chilled waterAir conditioning, condenser

waterAir lineAspirator, laboratoryAspirator, medicalAspirator, weedicide and

fertilizer sprayerAutoclave and sterilizerAuxiliary system, industrialAuxiliary system, surface waterAuxiliary system, unapproved

well supplyBoiler systemChemical feeder, pot-typeChlorinatorCoffee urnCooling systemDishwasherFire standpipe or sprinkler

systemFountain, ornamentalHydraulic equipmentLaboratory equipmentLubrication, pump bearingsPhotostat equipmentPlumber’s friend, pneumaticPump, pneumatic ejectorPump, prime linePump, water operated ejector


Sewer, sanitarySewer, stormSwimming pool

Fixtures withSubmerged Inlets

Description

Baptismal fountBathtubBedpan washer, flushing rimBidetBrine tankCooling towerCuspidorDrinking fountainFloor drain, flushing rimGarbage can washerIce makerLaboratory sink, serrated nozzleLaundry machineLavatoryLawn sprinkler systemPhoto laboratory sinkSewer flushing manholeSlop sink, flushing rimSlop sink, threaded supplySteam tableUrinal, siphon jet blowoutVegetable peelerWater closet, flush tank,

ball cockWater closet, flush valve,

siphon jet

Appendix B

Illustrations ofBacksiphonageThe following illustrates typicalplumbing installations wherebacksiphonage is possible.

BacksiphonageCase I (Fig. 44)

A. Contact Point: A rubberhose is submerged in a bedpanwash sink.B. Causes of Reversed Flow:(I) A sterilizer connected to thewater supply is allowed to coolwithout opening the air vent.As it cools, the pressure withinthe sealed sterilizer drops belowatmospheric producing avacuum which draws thepolluted water into the sterilizercontaminating its contents. (2)The flushing of several flushvalve toilets on a lower floorwhich are connected to an

undersized water service linereduces the pressure at thewater closets to atmosphericproducing a reversal of the flow.C. Suggested Correction: Thewater connection at the bedpanwash sink and the sterilizershould be provided withproperly installed backflowpreventers.

BacksiphonageCase 2 (Fig. 45)

A. Contact Point: A rubberhose is submerged in a labora-tory sink.B. Cause of Reversed Flow:Two opposite multi-storybuildings are connected to thesame water main, which oftenlacks adequate pressure. Thebuilding on the right hasinstalled a booster pump.

A

B B

B

A

B

FIGURE 44.Backsiphonage (Case 1).



B

A

Main

Gasoline

Water

APPENDIX B • 39

When the pressure is inad-equate in the main, the build-ing booster pump startspumping, producing a negativepressure in the main andcausing a reversal of flow in theopposite building.C. Suggested Correction: Thelaboratory sink water outletshould be provided with avacuum breaker. The waterservice line to the booster pumpshould be equipped with adevice to cut off the pumpwhen pressure approaches anegative head or vacuum.


A. Contact Point: A chemicaltank has a submerged inlet.B. Cause of Reversed Flow:The plant fire pump drawssuction directly from the citywater supply line which isinsufficient to serve normalplant requirements and a majorfire at the same time. During afire emergency, reversed flowmay occur within the plant.C. Suggested Correction: Thewater service to the chemicaltank should be providedthrough an air gap.


A. Contact Point: The watersupply to the dishwasher is notprotected by a vacuum breaker.Also, the dishwasher has a solidwaste connection to the sewer.B. Cause of Reversed Flow:The undersized main servingthe building is subject toreduced pressures, and thereforeonly the first two floors of thebuilding are supplied directlywith city pressure. The upperfloors are served from a boosterpump drawing suction directlyfrom the water service line.During periods of low citypressure, the booster pumpsuction creates negativepressures in the low system,thereby reversing the flow.C. Suggested Correction: Thedishwasher hot and cold watershould be supplied through anair gap and the waste from thedishwasher should dischargethrough an indirect waste. Thebooster pump should beequipped with a low-pressurecutoff device.


A. Contact Point: The gasolinestorage tank is maintained fulland under pressure by means ofa direct connection to the citywater distribution system.

B. Cause of Reversed Flow:Gasoline may enter thedistribution system by gravityor by siphonage in the event ofa leak or break in the watermain.C. Suggested Correction: Areduced pressure principlebackflow preventer should beinstalled in the line to thegasoline storage tank or a surgetank and pump should beprovided in that line.


A. Contact Point: There is asubmerged inlet in the secondfloor bathtub.B. Cause of Reversed Flow:An automobile breaks a nearbyfire hydrant causing a rush ofwater and a negative pressure inthe service line to the house,sucking dirty water out of thebathtub.C. Suggested Correction: Thehot and cold water inlets to thebathtub should be above therim of the tub.

CHEMICALS INC.

A

B



B

A


B

A

Main

Sewer

Dishwasher

High serviceLow service

Appendix C

The following presentsillustrations of typical plumbinginstallations where backflowresulting from backpressure ispossible.

BackflowCase I (Fig. 50)

A. Contact Point: A directconnection from the city supplyto the boiler exists as a safetymeasure and for filling thesystem. The boiler water systemis chemically treated for scaleprevention and corrosioncontrol.B. Cause of Reversed Flow:The boiler water recirculationpump discharge pressure orbackpressure from the boilerexceeds the city water pressureand the chemically treatedwater is pumped into thedomestic system through anopen or leaky valve.C. Suggested Correction: Asminimum protection two checkvalves in series should beprovided in the makeupwaterline to the boiler system.An air gap separation orreduced pressure principlebackflow preventer is better.

C. Suggested Correction:Each pier water outlet shouldbe protected against backflow.The main water service to thepier should also be protectedagainst backflow by an air gapor reduced pressure principlebackflow preventer.

BackflowCase 4 (Fig. 53)

A. Contact Point: A single-valved connection existsbetween the public, potablewater supply and the fire-sprinkler system of a mill.B. Cause of Reversed Flow:The sprinkler system is nor-mally supplied from a nearbylake through a high-pressurepump. About the lake are largenumbers of overflowing septictanks. When the valve is leftopen, contaminated lake watercan be pumped to the publicsupply.C. Suggested Correction: Thepotable water supply to the firesystem should be through an airgap or a reduced pressureprinciple backflow preventershould be used.

Illustrations ofBackpressure


A. Contact Point: Sewageseeping from a residentialcesspool pollutes the privatewell which is used for lawnsprinkling. The domestic watersystem, which is served from acity main, is connected to thewell supply by means of a valve.The purpose of the connectionmay be to prime the wellsupply for emergency domesticuse.B. Cause of Reversed Flow:During periods of low citywater pressure, possibly whenlawn sprinkling is at its peak,the well pump dischargepressure exceeds that of the citymain and well water is pumpedinto the city supply through anopen or leaky valve.C. Suggested Correction: Theconnection between the wellwater and city water should bebroken


A. Contact Point: A valveconnection exists between thepotable and the non potablesystems aboard the ship.B. Cause of Reversed Flow:While the ship is connected tothe city water supply systemfor the purpose of taking onwater for the potable system,the valve between the potableand nonpotable systems isopened, permitting contami-nated water to be pumped intothe municipal supply.

B

A

A

B

Citymain

Pump

To potablesystem

FIGURE 50.Backflow (Case 1).




ACME MILLS

SprinklerSystem

B

A

Chemical feederB

A


2xD

Pump

Ball check

Waste line

D

Appendix D

The following illustrations describe methods of providing anair gap discharge to a waste line which may be occasionally orcontinuously subject to backpressure.

Appendix E

Illustrations ofAir Gaps

Illustrations ofVacuum Breakers

To fire system

Float valvesNonpotable supply2xD

Potable supply

FIGURE 54.Air gap to sewer subject tobackpressure—force main.

FIGURE 55.Air gap to sewer subject tobackpressure—gravity drain.

FIGURE 56.Fire system makeup tank for adual water system.

Brass inset

Rubber sleeve

Air vent

AirAir enters herepreventing rise of

contaminated liquidsin fixtures

Vaccum closes gate

Cowl nut

Flush connection

FIGURE 57.Vacuum breakers.

FIGURE 58.Vacuum breaker arrangement foran outside hose hydrant.

Plan

“A” “A”

Exteriorbuilding wall

1" sleeve, sch. 40.

Hand wheel

I.P.S. hose adapter

Coupling M.I. galv.

Section “A” “A”½" or ¾" Ell. m. M. I. galv.

½" or ¾"nipple galv.

½" or ¾"gate valve

½" or ¾"sch. 40. galv.

½" or ¾"vacuum breaker

(By permission of Mr. Gustave J. AngeleSr., P.E. formerly Plant SanitaryEngineer, Union Carbide NuclearDivision, Oak Ridge, Tenn.)

2xDIndirect waste

Ball check

Support vanes

Horizontal waste

D

APPENDIX E • 41

Appendix F

Effective Opening Theminimum cross-sectionalarea at the point of watersupply discharge, measuredor expressed in terms of(1) diameter of a circle, or(2) if the opening is notcircular, the diameter of acircle or equivalent cross-sectional area.

Flood-Level Rim The edge ofthe receptacle from whichwater overflows.

Flushometer Valve A devicewhich discharges a prede-termined quantity of waterto fixtures for flushingpurposes and is actuated bydirect water pressure.

Free Water Surface A watersurface that is at atmo-spheric pressure.

Frostproof Closet A hopperwith no water in the bowland with the trap andwater supply control valvelocated below frost line.

Indirect Waste Pipe A drainpipe used to convey liquidwastes that does notconnect directly with thedrainage system, but whichdischarges into thedrainage system throughan air break into a ventedtrap or a properly ventedand trapped fixture,receptacle, or interceptor.

Plumbing The practice,materials, and fixturesused in the installation,maintenance, extension,and alteration of all piping,fixtures, appliances andappurtenances in connec-tion with any of thefollowing: sanitarydrainage or storm drainagefacilities, the ventingsystem and the public orprivate water-supplysystems, within oradjacent to any building,structure, or conveyance;also the practice andmaterials used in theinstallation, maintenance,extension, or alteration ofstorm water, liquid waste,or sewerage, and water-supply systems of anypremises to their connec-tion with any point ofpublic disposal or otheracceptable terminal.

Potable Water Water freefrom impurities presentin amounts sufficient tocause disease or harmfulphysiological effects.Its bacteriological andchemical quality shallconform to the require-ments of the USEPANational Primary Drink-ing Water Regulations andthe regulations of thepublic health authorityhaving jurisdiction.

Vacuum Any absolute pressureless than that exerted bythe atmosphere.


Glossary

Air gap The unobstructedvertical distance throughthe free atmospherebetween the lowestopening from any pipe orfaucet supplying water to atank, plumbing fixture, orother device and the flood-level rim of the receptacle.

Backflow The flow of water orother liquids, mixtures, orsubstances into thedistributing pipes of apotable supply of waterfrom any source or sourcesother than its intendedsource. Backsiphonage isone type of backflow.

Backflow Connection Anyarrangement wherebybackflow can occur.

Backflow Preventer A deviceor means to preventbackflow. BackflowPreventer, ReducedPressure Principle TypeAn assembly of differentialvalves and check valvesincluding an automaticallyopened spillage port to theatmosphere.

Backsiphonage Backflowresulting from negativepressures in the distribut-ing pipes of a potable watersupply.

Cross-Connection Any actualor potential connectionbetween the public watersupply and a source ofcontamination or pollution.

Vacuum Breaker A devicethat permits air into awater supply distributionline to preventbacksiphonage.

Water Outlet A dischargeopening through whichwater is supplied to afixture, into the atmo-sphere (except into an opentank which is part of thewater supply system), to aboiler or heating system, toany devices or equipmentrequiring water to operatebut which are not part ofthe plumbing system.

Water Supply System Thewater service pipe, thewater-distributing pipes,and the necessary connect-ing pipes, fittings, controlvalves, and all appurte-nances in or adjacent tothe building or premises.The water supply systemis part of the plumbingsystem.

Engineer's Guide to Cross Connection Control Quiz Ezekiel Enterprises, LLC

43

1. The contaminant enters the potable water system when the pressure of the polluted source__________ the pressure of the potable source.

o exceeds

o is less than

o equalso

2. Why do cross-connections hazards exist?

o Why do cross-connections hazards exist?

o Unaware plumbing installers

o Convenience without regard for hazard

o Inadequate Protection

o All of the aboveo

3. The Alabama incident of sodium hydroxide being back-siphoned into the water main was causeby who?

o Funeral home technician

o Truck driver

o Water plant employee

o Farmero

4. Propane gas in the water main was the result of which type of incident?

o Fracking

o A backyard barbeque

o Purging of propane tank

o Ship repair facilityo

5. Pesticides in the drinking water was caused by the simultaneous event of filling a pesticide truckwith water and what?

o Rapid increase in water pressure

o Water main break

o Cavitation in water main

o Lightning strikeo

6. Which chemical contaminated the water main due to a professional exterminator connecting agarden hose to a barrel of the chemical?

o Chlordane

o Hexavalent chromium

o Chromium

o Sodium Hydroxide


44

7. The office building incident in New jersey of cross-connection was attributed to what defect?

o Lack of fire protection on critical equipment

o All water facets being open via a test at the same time

o No backflow protection on make-up supply line to a hot-water storage tank

o Incorrectly sized water chillero

8. Back siphonage results in fluid flow in an undesirable or reverse direction. It is caused by what?

o Atmospheric pressure exerted on a pollutant liquid forcing it toward a potable water supply system that is under a vacuum

o Vacuum pressure exerted on a pollutant liquid forcing it toward a potable water supply system that is under pressure

o Absolute pressure being less than gauge pressure on the combined system

o Venturi effects on typical plumbing equipment and pipingo

9. The rate of pressure increase for water per foot of depth is how much? (aka pressure head)

o 0.433 psi

o 4.33 psi

o 14.7 psi

o 62.4 psio

10. One of the common occurrences of dynamically reduced pipe pressures is found where?

o On diverging sections of pipe

o On the outlet side of a pump

o On the suction side of a pump

o At piping elbowso

11. What is called the reversed flow due to backpressure?

o Back siphonage

o Backflow

o Hydraulic release

o All of the aboveo

12. How many basic type devices are available to correct cross-connections?

o One

o Six

o Hundreds

o Too numerous to specifyo


45

13. Which of the following devices protect against both back siphonage as well as backflow?

o Atmospheric vacuum breaker

o Barometric loop

o Pressure vacuum breakers

o Double check valveo

14. Which devices provides the maximum protection of all devices?

o Double check with intermediate atmospheric vent

o Double check detector check

o Reduced pressure principle backflow preventer

o Air gapo

15. What is the expected average pressure loss through a reduced pressure principle backflow?

o 5 to 10 psi

o 10 to 20 psi

o 25 to 50 psi

o 50 to 100 psio

16. What major prerequisite should be coordinated prior to any testing?

o Shutting down of the water supply

o Calibrating testing equipment

o Determining flow direction

o Holding a safety meetingo

17. Which of the following are types of test equipment?

o Differential pressure gauge

o Duplex gauge

o Bourdon gauges

o All of the aboveo

18. Who has the responsibility to ensure protection of the public health from cross connections?

o Plumbing inspectors

o Building managers

o Maintenance personnel

o All of the above


46

19. What common procedure is performed to assess that a facility is compliant to cross-connection control?

o Cross connection control survey

o Potable water analysis

o Meeting with the facility site engineer or supervisor

o Review of facility’s potable water drawingso

20. What device is recommended to be placed upstream of a backflow device to prevent device fouling due to debris?

o Differential pressure gauge

o Strainer

o Backflow connection

o All of the above

Documents

ME1260-Engineer's Guide to Cross Connection Control · The Engineer's Guide to Cross Connection Control course satisfies four (4) hours of professional development. The course is