Brian BenhamBiological Systems Engineering Center for Watershed Studies

Septic Systems Function and Maintenance

OutlineReview components, function

and maintenance of conventional gravity-flow septic system

Discuss septic system site considerationsIntroduce alternative

septic systemsBriefly review on-

site regulationsWater quality implications

associated with using on site systemsGeneral Septic System Dos and Don’ts

2

Typical System ComponentsHousehold Collection SystemSeptic TankEffluent Distribution

Distribution BoxPump/Dosing System

Drainfield / Absorption System

Replacement Area

3http://geoscape.nrcan.gc.ca/h2o/bowen/quality_e.php

Septic TankCompartmented tank or

series of tanksConcrete, fiberglass, polyethylene

Primary treatment – solids separation

4

Two Compartment Septic Tank

5Lesikar, 1999; On-site wastewater treatment systems, L-5234

Sludge

Distribution Box

6

Drain/Absorption Field

7http://www.thenaturalhome.com/infiltratorandpipe.jpg

Trench w/ gravel

8

Infiltration Chamber

9

How does septic system work?

10

What causes septic systems to fail?Problems:

Clogging of distribution system and/or drainfield by solids AND bacterial mats

Disruption of septic tank flora

Causes: Reduced hydraulic retention time

due to excessive solids/sludge build up in septic tank

Excessive flow into septic tank and drainfield (too much water, too often)

Use of harsh chemicals

Addition of oils/greases/fine particles that flow into and clog drainfield

11

Signs of septic system failureBad odors around the

drainfield especially after heavy water use or rainfall

Soggy soil, wet spots with lush green grass growth over drainfield or septic tank

Standing water in drainfieldSlow draining fixtures Plumbing back-ups High levels of coliform

bacteria or nitrate in nearby wells

12

Tips to keep septic system working…Reduce volume entering system

Use less water – consider low flow toilets, shower heads, etc.

Do laundry a little at a time – 1 to 3 loads a day.Reduce water softener recharge cycle

Perform system inspection regularly and pump septic tank when needed or on regular interval

Don’t use garbage disposalAvoid harsh cleaners; use all cleaners sparinglyMaintain good grass cover over drainfieldProtect drainfield from excess runoff

13

Practice Water Conservation

14

Objective Reduce volume of

water flowing into septic tank

Conserve water

OutcomeLonger retention time

(more opportunity for solids settling)

Longer usable life for drainfield

Reduced energy use

Action Typical Use Conservative Use

Toilet flushing 6 (old standard) 1.5-3 (low flow)

Tub bath 30 (half filled) 15 (quarter filled)

Shower (10 min.) 50 (5 gal/min flow) 25 (2.5 gal/min flow)

Shower (3 min.) 15 (5 gal/min flow) 7.5 (2.5 gal/min flow)

Laundry (top load) 50-60 (older models) 40 (newer models)

Laundry (front load) 33 (older models) 17-28 (newer models)

Source: University of Minnesota Cooperative Extension Service

Action Typical Use Conservative Use

Dishwashing (machine)

12-15 (old model regular cycle)

6-9 (new model regular cycle)

Dishwashing (hand) 16 (faucet rinse) 6 (basin rinse)

Teeth brushing 2 (faucet running)1/8 (wet brush,

brief rinse)

Hand washing 2 (faucet running) 1 (basin, brief rinse)

Shaving 3-5 (faucet running) 1 (basin, brief rinse)

Source: University of Minnesota Cooperative Extension Service

Septic Tank Pump OutFrequency

Depends on water use (volume of water entering tank) and material put into tank

Two rules of thumb Every 3 to 5 years When solids (sludge)

accumulation is 30 to 50% of tank volume.

15

Pump Out 101: Pumper should:

Note liquid level which can indicate leaks (too low) or problems with drainfield (too high)

Look for back flow from drainfield

Pump tank completelyCheck tank for signs of

damage

16

VA Dept. of Health FLASH module

17

http://www.vdh.state.va.us/EnvironmentalHealth/Onsite/howsystemsworks/septictank.htm

Septic Tank Pumping Frequency Based on Tank and Household Size

Household Size

(number of people)

1 2 3 4 5 6

Num

ber of Years

Tank S

ize (gallons)

750 9.1 4.2 2.6 1.8 1.3 1.0

1000 12.4 5.9 3.7 2.6 2.0 1.5

1250 15.6 7.5 4.8 3.4 2.6 2.0

1500 18.9 9.1 5.9 4.2 3.3 2.6

1750 22.1 10.7 6.9 5.1 3.9 3.1

2000 25.4 12.4 8.1 5.9 4.5 3.7

2250 28.6 14.0 9.1 6.7 5.2 4.2

2500 31.9 15.6 10.2 7.5 5.9 4.8

GET PUMPED! 18

RegulationsState-wide regulations address

acceptable materials and construction standards for septic system componentsSystem capacity

Tank/treatment unit Drainfield and replacement area

Location: minimum distances from buildings, wells, springs, etc.

Site suitability and assessment protocols

Chesapeake Bay Preservation ActRequires pump out every 5 years

19

Sizing Septic Tank

20

Tank size is function of amount of sewage generated and water use (rules of thumb)

Lesikar, 1999; On-site wastewater treatment systems, L-5227

Site and Soil AssessmentDepth to

GroundwaterBedrockImpermeable layers

Soil mottling (indicates high water table)

Permeability (too low and too high)

Adjacent featuresProperty lines, structures, wells,

springs, surface water, etc.

21

22Zipper, 2009; On-Site Sewage Treatment Alternatives, VCE448-407

Locating & Sizing DrainfieldPercolation (perc) tests

determine Permeability.

Must have sufficient, but not excessivly permeable soils.

Drainfield size is function of how much wastewater is generated and soil permeability.

Tighter (finer textured) soils require larger drainfields.

Slope must be considered.

23

Setback Distances

2412 VAC 5-610-10 et seq., Sewage Handling and Disposal Regulations

Alternatives: Mound SystemRaised drainfield; sand fill above the soil surface. Overcome site restrictions such as slowly permeable

soil, shallow permeable soil over creviced or porous bedrock, and permeable soil with high water tables.

Effluent is applied to system in timed doses using pump

25Zipper, 2009; On-Site Sewage Treatment Alternatives, VCE448-407

Alternatives: Mound System

26

Alternatives: Shallow-Placed SystemsSystems with drainfields within 18 inches of the surface

27

Low-pressure Distribution

Trickle IrrigationZipper, 2009; On-Site Sewage Treatment Alternatives, VCE448-407

Alternatives: Aerobic Treatment UnitATU is a mechanical system that treats

effluent using processes that require oxygenIncludes aeration chamber, a mechanical

agitator, and a sludge settling compartment.

28Zipper, 2009; On-Site Sewage Treatment Alternatives, VCE448-407

Alternatives: Constructed Wetland

29

VDH FLASH for pumped systemshttp://www.vdh.state.va.us/EnvironmentalHealth/Onsite/howsystemsworks/pumpsystem.htm

30

New Regulations for AOSSNew operation and maintenance requirements for owners

of alternative onsite sewage systems (AOSS)Annual inspections by a licensed AOSS operator.

Additional inspections depending on system complexityFirst inspection is due by April 7, 2011. Reports filed

electronically with VDH by the operator (inspector). Must maintain an Operations and Maintenance Manual and

operators log. Documents should transfer on sale. AOSS’s permitted after April 7, 2010 will have sampling

requirement to verify the performance.Local Health Department can provide additional dertails.

31

32

For help finding a Onsite Sewage Systems Operator, Call your Local Health Department

Septic Systems Costs Vary GreatlyCost vary primarily because of the type of system and

site specific factors (soil, slope, etc.)VA Department of Conservation and Recreation bases

cost share amounts in TMDL implementation watersheds on the following estimates

33

Pumpout $150 – 300

Repairs $300 – 4,000

Septic system replacement/installation $3,000 – 8,000

Septic system with pump $4,500 – 9,000

Alternative waste treatment systems $15,000 – 20,000

Connection to public sewer $2,000 – 6,000

Risks to Water QualitySurface and groundwater

contamination possible

Nitrogen Nitrogen in effluent

40 mg/L (approx.) 75%, ammonia; 25% organic  

Ammonium (NH4+ )

converted to Nitrate (NO3-)

NO3- mobile in both saturated and unsaturated soil conditions.

Limited risk contaminants Chlorides

Phosphorus

Emerging contaminants

34

Metals

Microorganisms

http://wrri.nmsu.edu/publish/watcon/proc51/mcquillan.pdf

Emerging ContaminantsPharmaceuticals and

Personal Care Products (PPCPs)USGS study – 139 streams in 30 states:

82 of 95 antibiotics, prescription & non-prescription drugs, steroids, & hormones were found in at least 1 sample

Surface and groundwater at risk

Current treatment technologies and monitoring do not target PPCPs

Fate and transport in soil and water unclear

Environmental/ health impacts unclear

Proper disposal is CRITICAL

35

Kolpin, D.W. et al. 2002. “Pharmaceuticals, hormones, & other organic wastewater contaminants in U.S. streams, 1999-2000: A national reconnaissance.” Environmental Science & Technology. 36(6):1202-1211

Septic Systems DosKnow where your septic system is.

Have your septic system inspected and pumped as needed.

Keep records of repairs, pumpings, inspections, permits

Use commercial cleaners and detergents in moderation. Mild detergent or baking soda is preferable.

Plant only grass over and near your septic system.

Keep water usage to a minimum.

Divert surface water (runoff, irrigation, etc.) away from the drainfield.

36

Septic Systems Don’tsDon’t treat your septic system as a trash can. Avoid

introducing fine/floating solids and material that are difficult to digest (avoid using garbage disposal).

Don’t drive or park vehicles on any part of your septic system. Doing so can compact the drainfield or damage the pipes, tank, or other septic system components.

Don’t build or pave over drainfield or your replacement area.

37

Add VT pub

38

www.epa.gov/owm/septic/pubs/homeowner_guide_long.pdf http://pubs.ext.vt.edu/448/448-407/448-407.pdf

39

Brian BenhamExtension Specialist

Website: www.wellwater.bse.vt.edu

Email: benham@vt.edu

Ph: 540-231-5705