Home Inspector Secrets

3Chapter # Chapter Title

IP A R T O N E

SUPPLY PLUMBING

In Part I we look at how water gets into the house. We look at both public and pri-vate supply systems. Although we can’t see much of them during inspections, we’lltalk about the service pipes or water entry pipes that bring the water up to the house.We’ll also look more closely at the piping we can see inside the house on the supplyside. We will talk about the things that cause supply plumbing problems, such asleaks and low water pressure.

IP A R T O N E

DHI_Book06-Part-1.qxd 21/05/2003 12:28 Page 3

DHI_Book06-Part-1.qxd 21/05/2003 12:28 Page 4

5

PRINCIPLES OFSUPPLY PLUMBING

L E A R N I N G O B J E C T I V E S

At the end of this chapter you should be able to:

� describe functional flow in one sentence

� describe in three sentences the flow of water through the house from its pointof entry to its point of exit, including the function of the vent piping

� list three things that can go wrong with supply piping

� list four factors that affect the pressure or flow at a fixture

1C H A P T E R 1

DHI_Book6_C01.qxd 21/05/2003 12:29 Page 5

6 Part I Supply Plumbing

1.1 HOW SUPPLY PLUMBING WORKSPotable Water We need clean water readily available at several locations throughout the house. We

capture the water in piping to keep it where we want it and then push on it hardenough to move it through the pipes. If we do it right, we’ll always have water avail-able when we open a faucet. We call the clean water potable, which means we canuse it for drinking, cooking, and washing.

1.2 THE SOURCEPublic or Private Water Supply The source of water for a house is either a municipal supply system or a private

system such as a well and pump. Private systems can also be from lakes, ponds,rivers, cisterns, etc. For the most part, the sources are very similar, and an investi-gation of the sources is beyond the scope of a professional home inspection. Eitherthe municipal or the private water supply system is assumed to provide us with acontinuous supply of clean water at a relatively constant pressure. Since the munic-ipal system is more common, let’s use that as our example.

Water Delivered Through a wonderful series of pipes, pumps, and sometimes big, tall gravitytanks, the municipality is able to deliver the water right to your front door. All wedo is open the tap and use it. So what could possibly go wrong?

1.3 WHAT CAN GO WRONGThere are three things that can go wrong.

1.3.1 LeaksSometimes we get the water when or where we don’t want it. We call these leaks.They range from an annoying dripping faucet to a split pipe that floods the house.

1.3.2 Not Enough WaterThe next thing that goes wrong is when we don’t get enough water. People areoften confused by this condition. Some say they don’t have enough pressure, otherssay they don’t have enough flow, and still others say they don’t have enough volume.These are all different ways of saying the same thing. From a practical standpoint,if you’re having a shower when somebody flushes the toilet and you don’t have waterat the shower any more, there is a supply problem. Sometimes you just run out ofcold water when the toilet flushes and get scalded. Sometimes you run out of hotwater. Neither of these makes you happy. We’ll call these flow/pressure problemsto satisfy everyone.

1.3.3 Dirty WaterThe water is dirty. The water quality may be poor because of a problem with themunicipal supply system or a well and pump system, for example. The water mayalso be dirty because it’s accidentally mixed with the waste water in the house.


7Chapter 1 Principles of Supply Plumbing

All of these situations are dangerous. Some are easy to find and others are justabout impossible.

We’ll talk about where and why leaks occur later. Frankly, that part’s pretty easy.Looking for dirty water can be easy, but we’ll get to that later. The concept ofhaving enough water is a little more complex. Let’s spend some time on it.

1.4 WATER SUPPLY—PRESSURE AND FLOWWe hate formulas, and we don’t like graphs any better, so let’s get through this with-out too many of either.

Factors Affecting Supply The amount of water available at the tap depends on several things (Figure 1.1),including—

� how big the pipe is

� how smooth the inside of the pipe is

� how straight the pipe is

� how hard it is being pushed from behind (what’s the static pressure?)

� how much water we are trying to move (what flow are we looking for, in gallons per minute?)

� are we pushing it uphill? how high?

F I G U R E 1.1 Factors Affecting Supply of Water

More water Less water

Pipe size

Smoothness ofinside of pipe

Number ofchanges indirection

Pressrue

Height

Pressure Pressure



The water supply for any fixture in any house cannot be described just in termsof pressure (in pounds per square inch or kilopascals), volume (gallons or liters),or flow rate (gallons per minute or liters per second). It is best described as a simplegraph that looks something like Figure 1.2.

The Greater the Flow, When there is no water flowing, there will be lots of pressure ready to push waterthe Lower the Pressure out of the pipe. As we open the tap and water starts to flow, the pressure will be

reduced. The more you open the tap, the more water flows. (Note: The flow is arate, usually measured in gallons per minute.) The more water that flows, the lowerthe pressure will drop. The rate at which pressure drops as flow increases establishes

Flat Curves Are Good the profile for the water supply to that tap. A flatter curve is better because the flowSteep Curves Are Bad increases without losing much pressure. The steeper the curve, the worse it is. As

soon as we start to flow a little water, we lose pressure very quickly. When the pres-sure drops down to zero, the water will just trickle out of the tap or stop flowingaltogether.

Static Pressure Let’s talk about two different kinds of pressure. Static pressure is the pressureexerted by the water on the walls of the pipe when no water is flowing. There willbe no flow as long as the taps are closed. Assuming that the pipe is horizontal, no matterwhere you measure the static pressure along that pipe, you would have the same pres-sure reading (Figure 1.3). If that pressure was 60 psi (pounds per square inch) wherethe pipe first came into the house, it would also be 60 psi right at the back of the house.

Pressure Loss Due to Friction Once water starts to flow, the water moving through the pipe uses some of itsenergy to push past the pipe surface, no matter how smooth the pipe is. This con-sumes energy and reduces the pressure available to push water out the end of thepipe. This pressure loss due to friction occurs at every point along the pipe. Whenwater starts to flow through a pipe, the pressure is highest at the source and decreasesevery inch along that pipe. The pressure would be lowest right at the tap.

Lose 7 psi over 100 Feet If we wanted to move 3 gallons per minute (gpm) through 1/2-inch-diameter pipe,100 feet long, we might lose about 7 psi of pressure. If the pressure at the beginning

F I G U R E 1.2 Pressure Drop as Flow Rate Increases

Note:Pressure drop shownis across an equivalentpipe length of 100'

Each fixture in the housewill have a different profile

1/2" Pipe

3/4" Pipe

Flow rate (gallons per minute)

1 2 3 4 5 6 7 8 9 10

Pre

ssur

e dr

op (

PS

I)

40

35

30

25

20

15

10

5

0



of the pipe is 60 psi, the pressure at the end would be 53 psi. Flows (or flow rates)are measurements of the volume of water that comes out of the tap every minute.If a faucet has a flow of 3 gpm, that means you could fill a 3-gallon bucket if youleft the tap open for 1 minute.

Flow Constant Looking at our pipe, we would have 3 gpm coming out of the tap. We would alsoAnywhere Along Pipe have 3 gpm flowing past any point along the pipe. To help understand this, let’s look

at it this way: If we want to get 3 gpm out of the end of the pipe, we have to put3 gpm into the front of the pipe. The water can’t escape as it goes through the pipe,so the rate at which we dump it in at one end must be the rate at which it comes outthe other end.

Pressure Drops To summarize, as water is flowing through a pipe, the pressure drops as we movealong the pipe and the flow remains constant.

Curve Depends We were looking at a 100-foot pipe earlier. If we flow 3 gpm through that sameon Length of Pipe 1/2-inch-diameter pipe but make it 200 feet long, we will lose 14 psi (we lost 7 psi

in 100 feet, so we’ll lose another 7 psi in the next 100 feet). This means that if thepressure at the beginning of the pipe was 60 psi, it would be 46 psi at the end wherethe tap was open.

If we go back to our graph for a minute, let’s look at these two scenarios. In thefirst scenario, we have a static pressure of 60 psi with no water flowing. In the sit-uation where we have 100 feet of pipe, we have a pressure of 53 psi with 3 gpm flow-ing. In the second instance, where we have 200 feet of pipe, we also have a staticpressure of 60 psi with no water flowing. However, with 3 gpm flowing, the pres-sure is only 46 psi. The two different pipe layouts have two different curves becauseof the different lengths, even though they are in the same house, connected to thesame supply with the same diameter pipe.

The same thing works the other way around. To use the same example, if westarted with 60 psi and wanted to make sure we ended up with 50 psi, it would worklike this. In the first example, where we have 100 feet of 1/2-inch-diameter pipe, wecould run 3.5 gpm through the pipe and end up with 50 psi at the tap. However, wherewe have 200 feet of pipe, we could only run 2.4 gpm through the pipe to end up with

F I G U R E 1.3 Static Water Pressure

When no water is flowing, the static pressurewill be the same at all points along the pipe(that are at the same elevation)

60 psi(static)

From citywater supply

60 psi(static)

60 psi(static)

Basin


50 psi at the end. With the longer pipe, we have to flow less water if we want to endup with the same pressure at the tap.

Static Pressure Readings Again, the curve representing each tap is different, even in the same house at theDon’t Tell Story same elevation, because of the differences in pipe length. It should be clear now that

the static pressure doesn’t tell you very much about the overall water supply. Somepeople feel that a high static pressure is good, but it is not a guarantee of good watersupply. It’s one reason that many home inspectors don’t bother to measure the staticpressure. What you’re looking for is a system that does not lose much pressure aswe flow water.

Now let’s go back and look at how the four factors we talked about earlierimpact how much water is available at the tap.

1.5 FACTORS AFFECTING WATER FLOW1.5.1 Pipe Size

Big Pipes Are Better The first thing we talked about was the pipe itself: how big is it, how smooth and howstraight? It’s obvious to most people that the bigger the pipe, the more water thatyou can move through it. What’s not so obvious is how dramatic this is. For exam-ple, changing the pipe diameter from 1/2 inch to 3/4 inch makes a very large differ-ence. Many would say that a 3/4-inch pipe is 50 percent larger than a 1/2-inch pipe,and you should be able to get 50 percent more water through it. Actually, a 3/4-inch-diameter pipe is 225 percent of a 1/2-inch-diameter pipe in cross-sectional area(Figure 1.4)! If you’re keen, you can do the math. The area of a circle is pi × r2. Piis roughly 3.14. The radius of a 1/2-inch-diameter pipe is roughly 1/4 inch. The radiusof a 3/4-inch-diameter pipe is roughly 3/8 inch.

Much Better In practice, the difference is even more dramatic than the cross-sectional areawould suggest. If you consider 100 feet of 1/2-inch-diameter pipe, you will lose 10psi of pressure running 3.5 gpm through the pipe. For 3/4-inch-diameter pipe, you


F I G U R E 1.4 3/4-Inch Pipe Is More than Twice as Big as 1/2-inch Pipe!

r = radius = 0.375"

r = radius = 0.25"

r1/2"

Dia

met

er

1/2" Pipe

Cross sectional area= pi × r2

= 3.14 × (0.25)2

= 0.2 square inches

Cross sectional area= pi × r2

= 3.14 × (0.375)2

= 0.44 square inches

r

3/4" Pipe

3/4"

Dia

met

er



will lose 10 psi when you flow 9.4 gpm through it. The cross-sectional area of a 3/4-inch pipe is 225 percent of a 1/2-inch pipe, but the flow through a 3/4-inch-diameterpipe is 270 percent of the flow of a 1/2-inch pipe with the same pressure loss!

Rusted Pipes Are Bad We now have a pretty good sense of how important pipe diameter is. This should give you some appreciation to how little water flows through rusted galvanizedsteel pipes, for example. Not only does the surface become considerably rougher,which reduces flow (or increases pressure loss due to friction, whichever way youthink of it), but it also reduces the pipe diameter. This dramatically reduces theability of the pipe to move water. The profile or curve of a faucet fed by rusted gal-vanized steel piping, for example, becomes steeper with time (Figure 1.5).Homeowners become less and less happy with the rate of flow available at anygiven pressure.

Replacing Pipes To Changing any piece of pipe along that 100-foot length will help. Since pressure isImprove Flow lost pushing water past every inch of pipe along the way, if we only changed half

the pipe to 3/4 inch we would still enjoy a benefit. For example, if we wanted to flow61/2 gallons of water through 100 feet of 1/2-inch-diameter pipe, we might lose 30 psi.

Lose 15 psi in If we started with 60 psi at the beginning of the pipe, we’d end up with 30 psi at First 50 Feet the end of the pipe. If we put a gauge at the 50-foot mark, it would read approxi-

mately 45 psi because we’d lose 15 psi along the way. (Again, 6.5 gpm would beflowing past any point along the pipe.)

Lose 3 psi in Now, if we changed the first 50 feet of that pipe from 1/2 inch to 3/4 inch, we wouldFirst 50 Feet be much better off. Instead of losing 15 psi through that 50 feet, we’d lose about 3

psi. If we started with 60 psi, we’d still have 57 psi at the 50-foot mark. From that pointon, we’d lose 15 psi again, yielding 42 psi at the tap, instead of the 30 psi we got ear-lier. We’re better off than before, even though we didn’t change all of the pipe.

Changing Any Part A lot of people think you have to change the upstream (first) section of pipe to of the Pipe Helps avoid a bottleneck problem. Let’s try it the other way. If we changed the last 50 feet

from 1/2 inch diameter to 3/4 inch, what would happen? The first 50 feet of pipe wouldlook like it did originally. If we started with 60 psi and flowed the same amountof water, we would lose 15 psi. A gauge at the 50-foot mark would read 45 psi.

F I G U R E 1.5 Galvanized Steel Pipe

Leak

Leak

Rusting of galvanized pipe can greatly reduce waterpressure and will eventually cause leaks as rust createsholes in the pipe walls

Problems are likely to occure soonest on pipes carrying hotwater, horizontal pipes and at threaded (thinner) sections

Rust Rust

Cross section

Galvanized pipe



Now, if we changed the last 50 feet of pipe to 3/4 inch we’ll only lose 3 psi throughthat part. The result at the tap is going to be the same flow (about 61/2 gpm), with42 psi. As you can see, it doesn’t make any difference whether we replace theupstream or downstream section of pipe (Figure 1.6)!

People sometimes tell us that it doesn’t make sense to change the piping insidethe house until the pipe from the street to the house is replaced. We’ve just shownthat that is not true. Increasing any piece of pipe in the entire system will improvethe water supply. The more pipe we change, the better it gets.

Elbows Are Costly We have been talking about straight pipes. What happens if you make the waterchange direction? Elbows, tees, etc, consume considerable energy (create pressureloss due to friction). Each elbow represents several equivalent feet of pipe length.Convoluted piping systems have lower water supply profiles (Figure 1.7).

1.5.2 Static PressureStatic Water Pressure How hard the water is being pushed (the pressure available at the source) does have

an effect on how much water is available. As you can see, the starting point for allof these curves is the static pressure with no water flowing. Up to a point, the higherthe static pressure, the better off we are. Remember, though, that a high static pres-sure won’t eliminate a problem of pressure loss due to friction.

80 psi Is Maximum Beyond about 80 psi, higher pressure is not helpful. Static pressures in excess of80 psi are hard on fixtures and faucets. This typically results in frequent leakage prob-lems. As a result, residential systems with static pressure in excess of 80 psi usu-ally have a pressure regulator where the water comes into the house (Figure 1.8).The regulator is usually installed just downstream of the main water shutoff valveso that if you have to work on the regulator, you can shut the water off. Incidentally,the warranties of some appliances and water heaters are voided if the pressure isabove 80 psi.

F I G U R E 1.6 Downstream versus Upstream Pipe Replacement

Installing larger diameter piping in the downstream sectionsis just as effective as replacing the upstream sections

Fromstreet

Fromstreet

Flow Flow

FlowFlow

60PSI

60PSI

57PSI

45PSI

42PSI

42PSI

50 Feet(pressure drop = 3 PSI)




Atfixture

Atfixture

3/4" Pipe

3/4" Pipe

1/2" Pipe

1/2" Pipe



F I G U R E 1.7 Elbows and Tees Reduce Pressure

35PSI

32PSI

Basin

Water supplyfrom street

Each elbow and tee creates apressure loss (due to friction)equivalent to several feet of pipe

Convoluted piping arrangementscan reduce water supply

F I G U R E 1.8 Pressure Regulator Required

Residential systems with staticpressure in excess of 80 PSIusually have a pressure regulator

Pressure regulator(maximum 80 PSI)

Footing

Supply plumbingfrom street

Floor drain

Mainwatershut offvalve Basement

Pressure reliefdischarge pipe

A strainer should beinstalled upstream(these are often partof the regulator)

Watermeter

Pressure relief valvemay be required(typical setting—150 PSI)

Fou

ndat

ion

wal

l



F I G U R E 1.9 Constant Water Flow (Velocity) Can Wear Out Pipes

Hot water recirculating systems can prematurely wearout thin wall (type “M”) copper piping because wateris constantly flowing through the pipes

Floor framingCold

Cold

Hot

Hot

Hot water recirculating loop

Checkvalve

Hot waterrecirculatingpump

Gas

Gaswaterheater

Mainshut offvalve Basement

Crosssection

Fou

ndat

ion

wal

l

Strainers, Pressure Pressure regulators should have a strainer installed upstream to prevent sediment Relief, and Bypasses buildup. Regulators in some jurisdictions must also have some means of relieving

pressure in the house system. A pressure relief valve set at no more than 150 psi mayhave to be provided, or the regulator may have an integral bypass.

Excessive Velocity Another issue related to high water pressure is water velocity. In residential systems,Wears Out Pipes the relatively small pipe diameters (typically 1/2 and 3/4 inch) have a practical limit to

the velocity of water that can move through them. Water that moves too quickly canwear pipes prematurely, particularly the thin wall (Type M) copper piping that is widelyused (Figure 1.9).

Some plumbing authorities feel that the typical water velocities of 8 to 10 feetper second are too high and that a more appropriate design velocity is about 4 feetper second. Larger diameter piping allows for lower velocities. You can move thesame number of gallons per minute with lower velocities through larger pipes.However, this discussion carries us beyond the Standard home inspection and weshould leave it there. You won’t be able to judge water velocity during a typical homeinspection.

1.5.3 The Volume of Water We Are Trying to MoveThe More That Flows, The water supply available to any faucet is reduced if water is flowing elsewhere the Worse It Gets in the house. The shower may work perfectly until someone flushes a toilet. In

almost any house, if you get enough other fixtures flowing, you adversely affect theperformance of the shower. This makes perfect sense if we go back to the watersupply profile curve. The more water that flows through the pipes, the greater the



pressure drop. If you flow enough water through the pipes, the pressure will dropto a point where it cannot push water out through the shower nozzle effectively andmay not be able to keep the shower diverter open. In severe cases, the showerdiverter will relax, and water will come out the tub spout but not the showerhead.

Look at a Garden Hose More flow means less pressure. Less flow means higher pressure. Consider a garden hose. If we take a garden hose without a nozzle on the end of it, water willplop out of the hose and fall to the ground. We wouldn’t be able to spray someone15 feet away with the water coming out of the hose. We would, however, be able tofill up a bucket fairly quickly.

Reduced Flow If we put a thumb over the end the hose and just let a little bit of water by, we are Reduces Friction Loss reducing the flow rate (gpm) and raising the pressure at the nozzle. Because only a

small amount of water is moving past every point along the pipe, there is consid-erably less pressure loss due to friction.

Less Friction Loss Means Now we have lots of pressure at the end of the hose and we can easily squirt More Pressure at End of Pipe someone 15 or 20 feet away. If we could get our thumb to completely stop the water

flow, the static pressure at the end of the garden hose would be the same as the citywater pressure at the street.

Pressure not Important for From this example, it’s easy to see that the larger the flow rate, the lower theFilling Buckets pressure. If we wanted to fill up that bucket we talked about, we’re better off to leave

our thumb off the end of the hose. We’ll get more gallons per minute flowing outof the hose (at a lower pressure). If we put some liquid soap in the bucket and wantto create enough force to make it bubble, we can put our thumb back over the endof the hose. This won’t deliver water as quickly in terms of gallons per minute, butit will deliver water at a high pressure.

Pressure Important for This analogy works very well in the bathroom as well. To prepare a bath, we Showers but not Baths would use the tub spout because it delivers more gallons per minute and the tub will

fill up quickly. We wouldn’t want to have a shower under the tub spout though, becausethere isn’t much pressure.

Showers Are High Using the showerhead delivers water at a higher pressure but a lower flow rate. Pressure, Low Flow A shower is great for rinsing shampoo out of our hair because of the velocity that

results from the higher pressure. A showerhead would be a poor way to fill a bath-tub though because it would take much longer than using the tub spout.

Water-Saver Showerheads There are currently many water-saver fixtures on the market, including water-saver showerheads. These simply have smaller and/or fewer holes than conven-tional showerheads. As a result, they deliver slightly higher pressure but fewer gal-lons per minute. They provide a nice hard shower without using as much water.

More Fixtures, More Pressure As more and more water is being used by various fixtures at one time, the pres-Drop, Less Flow sure and flow rate of water supply available at each fixture will decrease. The total

water flow through the water entry pipe will increase with each additional fixtureturned on, but all the other fixtures will suffer. Houses with more people and morebathrooms are likely to suffer from poor water supply.

1.5.4 Pushing Water UphillPushing Water Uphill We’ve not yet talked about moving water vertically. Energy is required to move the

water higher. It takes 0.434 psi to raise water 1 foot. Conversely, 1 psi will raise water2.31 feet (Figure 1.10). If water enters the basement at 60 psi static pressure, there willbe 60 psi pressure near the basement floor. To move up through the basement, throughthe first floor, and to the shower on the second floor, we might have to push the waterup 20 feet. This would result in a pressure loss of between 8 and 9 psi (20 × 0.434).



Lower Static Pressure If the static pressure at the basement is 60 psi, the static pressure at the secondon Upper Stories floor fixture is roughly 52 psi. Again, you can see how the profiles of the water supply

at fixtures in houses vary, depending on how high the fixture is. This helps explainwhy it is best to test the plumbing fixtures at the highest point in the house. This isthe toughest test because that’s where the static pressure is lowest. It’s usually alsowhere the pipe length is greatest, from the source to the faucet, so we’ll have themost friction loss as well.

Basement While people may not enjoy living in a basement apartment, at least they have Showers Best the best water supply system in the house!

1.5.5 SummaryA Practical Flow Test Fortunately, home inspectors don’t have to do many calculations. We simply flow

a number of fixtures simultaneously and visually observe the pressure drop. It’s help-ful to show clients how the shower will perform with one, two, and three fixturesflowing. Your clients can determine for themselves whether the performance isacceptable.

People’s Expectations Vary We have found that people coming from old houses expect relatively low watersupply profiles and are not surprised by the pressure drop at the shower when otherfixtures are operating. People moving from high-rise buildings are often dismayed bythe same water supply profile that another client found perfectly acceptable.

Improving the Water Supply Where the water supply profile is not acceptable to the client, there are several things they can do. Sometimes the course of action is obvious. Other times, we

F I G U R E 1.10 Pressure Decreases with Height

47PSI

51PSI

55PSI

58PSI

60PSI

1 PSI will makewater rise 2.31 feet

30 ft.

27 ft.

21 ft.

18 ft.

12 ft.

9 ft.

0 ft.

Always test thewater pressure atthe highest point inthe house to get themost meaningfulresults

Cross section

3rd Floor

2nd Floor

1st Floor



simply have to say that further investigation is needed to determine which of sev-eral factors is contributing most heavily to the condition.

Old Steel Pipes A common situation is the presence of galvanized steel (usually 1/2-inch diameter)supply piping. This piping will almost always be near the end of its life (since it lasts40 to 60 years and it hasn’t been used in homes since the early 1950s). Even if it’snot leaking, the interior diameter of the pipe is usually reduced by rusting.

Causes of Poor Pressure/Flow The water supply may be less than ideal for a number of reasons. These reasonsmay apply to the service piping that brings the water from the city main to thehouse (or from the well, lake, or river to the house) and to the distribution pipingwithin the house. Let’s look at some of the causes.

1.6 CAUSES OF POOR PRESSURE/FLOW1.6.1 Undersized PipingIn some old houses, the supply piping diameter may be as small as 3/8 inch. In newhouses, 3/4 inch is considered minimum. In large houses or houses with more thanthree bathrooms, many jurisdictions call for a 1-inch pipe. This pipe diameter oftenis reduced once the water splits up into a hot and cold distribution system. Forexample, a 3/4-inch line may come into the house and run to the inlet of the waterheater. The outlet of the water heater will typically be 1/2-inch diameter, and the restof the cold water distribution piping will also be 1/2-inch diameter (Figure 1.11). Thisis a common and acceptable arrangement.

F I G U R E 1.11 Larger Diameter Pipe to Water Heater

Cross section

Fou

ndat

ion

wal

l

Gas

Gaswaterheater

Mainshut offvalve

Cold Hot

Floor framingCold

Hot

3/4" Copper pipe

1/2" Copper pipe

Basement



1.6.2 Rusted PipingGalvanized steel piping is notorious for rusting on the interior. It will eventually leakthrough, usually at the threaded joints, and cause leakage, but before this, the waterpressure will drop. The rough surface creates friction loss, and the accumulation ofrust on the inside of the pipe restricts the flow by reducing the diameter of the pipe.

Some people say you have to replace all the pipe to make a difference. That’snot true. For every foot of pipe that is replaced, you will enjoy some improvementin pressure and flow.

Horizontals Only If someone is only going to replace some of the piping, it makes sense to do thehorizontals, which tend to rust more quickly than the risers (vertical pipes).

Hot Water First It also makes more sense to do the hot water piping before the cold water pipingsince the rusting is a chemical reaction that happens more quickly at higher tem-peratures.

1.6.3 ObstructionsThere may be obstructions in the pipe itself. Obstructions can also be lodged invalves. Water meters, pressure regulators, water softeners, and other treatment devicesall present obstructions to flow and can trap foreign materials. A sludge build-up ina water heater will cause poor pressure on the hot water side but not the cold side.

Closed Valves, Crimped, A partially closed valve presents an obstruction to water flow. Piping that is Damaged crimped or mechanically damaged effectively reduces the pipe diameter, and the

low of water.

1.6.4 LeakingIf the water entry pipe is leaking outside the house, the flow and pressure inside thehome will be reduced. In most cases, this will be noticed, but if the water leakingfrom the pipe is carried away quickly from free draining soil or a storm sewer, forexample, this may go undetected.

1.6.5 Excess Pipe LengthThe amount of pressure drop is dependent on pipe length. The longer the pipe, the morepressure loss there will be due to friction as the water flows through the pipe. Housesset well back from the street or a considerable distance from a well, river, or lake, forexample, may have low water pressure because of the long supply piping runs.

The distribution piping runs in the house can be long as well, further reducingflow and pressure available at the faucets. Elbows and tees are each equivalent toseveral feet of pipe. Convoluted systems suffer as a result.

1.6.6 Elevation LossesHouses built well above street level or at the top of a hill may have lower pressure andflow than houses near the bottom of a hill or houses built below street level. We havetalked already about how we lose pressure when pushing water uphill. The staticpressure will be slightly less on the second story than it is on the first. Pressure onthe third floor will be slightly lower than on the second.


CHAPTER REVIEW QUESTIONSAnswer the following questions on a separate sheet of paper, then check your resultsagainst the answers provided in Appendix F. If you have trouble with a question,refer back to the chapter to review the relevant material.

1. What are three things that go wrong with water supply?

2. List at least four things that affect the volume of water at the tap.

3. Describe briefly how pressure and flow in a plumbing supply system are related.

4. What is static pressure?

5. Why is static pressure not a particularly good indicator of pressure in the house?

KEY TERMS


static pressure flow rate pressure


Documents

Home Inspector Secrets