Septic Systems
Function and Maintenance
Brian Benham
Biological Systems Engineering
Center for Watershed Studies
Outline
 Review components, function
and maintenance of conventional
gravity-flow septic system
 Discuss septic system site
considerations
 Introduce alternative
septic systems
 Briefly review
on-site regulations
 Water quality implications
associated with using on site systems
 General Septic System Dos and Don’ts
2
Typical System Components
 Household Collection System
 Septic Tank
 Effluent Distribution
 Distribution Box
 Pump/Dosing System
 Drainfield /
Absorption System
 Replacement Area
http://geoscape.nrcan.gc.ca/h2o/bowen/quality_e.php
3
Septic Tank
 Compartmented tank or
series of tanks
 Concrete, fiberglass, polyethylene
 Primary treatment – solids
separation
4
Two Compartment Septic Tank
Sludge
Lesikar, 1999; On-site wastewater treatment systems, L-5234
5
Distribution Box
6
Drain/Absorption Field
http://www.thenaturalhome.com/infiltratorandpipe.jpg
7
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 failure
 Bad 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 drainfield
 Slow 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 disposal
 Avoid harsh cleaners; use all cleaners sparingly
 Maintain good grass cover over drainfield
 Protect drainfield from excess runoff
13
Practice Water Conservation
 Objective
 Reduce volume of
water flowing into
septic tank
 Conserve water
 Outcome
 Longer 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)
Action
Laundry
(front load)
Use
33 Typical
(older models)
Conservative
Use
17-28
(newer models)
Dishwashing
12-15 (oldExtension
model Service
Source:
University of Minnesota Cooperative
(machine)
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
14
Septic Tank Pump Out
 Frequency
 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 completely
 Check tank for signs of
damage
16
VA Dept. of Health FLASH module
http://www.vdh.state.va.us/EnvironmentalHealth/Onsite/howsystemsworks/septictank.htm
17
Septic Tank Pumping Frequency
Based on Tank and Household Size
Household Size
(number of people)
2
3
4
5
6
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!
Number of Years
Tank Size (gallons)
1
18
Regulations
 State-wide regulations address
acceptable materials and construction
standards for septic system components
 System capacity

Tank/treatment unit

Drainfield and replacement area
 Location: minimum distances from
buildings, wells, springs, etc.
 Site suitability and assessment protocols
 Chesapeake Bay Preservation Act
 Requires pump out every 5 years
19
Sizing Septic Tank
 Tank size is function of amount of sewage
generated and water use (rules of thumb)
Lesikar, 1999; On-site wastewater treatment systems, L-5227
20
Site and
Soil Assessment
 Depth to
 Groundwater
 Bedrock
 Impermeable layers
 Soil mottling
(indicates high water table)
 Permeability
(too low and too high)
 Adjacent features
 Property lines, structures, wells,
springs, surface water, etc.
21
Zipper, 2009; On-Site Sewage Treatment Alternatives, VCE448-407
22
Locating & Sizing Drainfield
 Percolation (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
12 VAC 5-610-10 et seq., Sewage Handling and Disposal Regulations
24
Alternatives: Mound System
 Raised 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
Zipper, 2009; On-Site Sewage Treatment Alternatives, VCE448-407
25
Alternatives: Mound System
26
Alternatives: Shallow-Placed Systems
 Systems with drainfields within 18 inches of the surface
Low-pressure Distribution
Trickle Irrigation
Zipper, 2009; On-Site Sewage Treatment Alternatives, VCE448-407
27
Alternatives: Aerobic Treatment Unit
 ATU is a mechanical system that treats
effluent using processes that require oxygen
 Includes aeration chamber, a mechanical
agitator, and a sludge settling compartment.
Zipper, 2009; On-Site Sewage Treatment Alternatives, VCE448-407
28
Alternatives: Constructed Wetland
29
VDH FLASH for pumped systems
http://www.vdh.state.va.us/EnvironmentalHealth/Onsite/howsystemsworks/pumpsystem.htm
30
New Regulations for AOSS
 New operation and maintenance requirements for owners
of alternative onsite sewage systems (AOSS)
 Annual inspections by a licensed AOSS operator.
Additional inspections depending on system complexity
 First 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
For help finding a Onsite Sewage Systems Operator, Call your Local Health Department
32
Septic Systems Costs Vary Greatly
 Cost 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
Pumpout
Repairs
$150 – 300
$300 – 4,000
Septic system replacement/installation
$3,000 – 8,000
Septic system with pump
$4,500 – 9,000
Alternative waste treatment systems
Connection to public sewer
$15,000 – 20,000
$2,000 – 6,000
33
Risks to
Water Quality
 Surface and groundwater
contamination possible
 Nitrogen
 Nitrogen in effluent
40 mg/L (approx.)
75%, ammonia; 25% organic
 Ammonium (NH4+ )
converted to Nitrate (NO3-)
http://wrri.nmsu.edu/publish/watcon/proc51/mcquillan.pdf
 NO3- mobile in both saturated and unsaturated soil conditions.
 Limited risk contaminants
 Chlorides
 Metals
 Phosphorus  Microorganisms
 Emerging contaminants
34
Emerging Contaminants
 Pharmaceuticals and
Personal Care Products (PPCPs)
 USGS study – 139 streams in 30 states:
82 of 95 antibiotics, prescription & nonprescription 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
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
 Proper disposal is CRITICAL
35
Septic Systems Dos
 Know 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’ts
 Don’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
www.epa.gov/owm/septic/pubs/homeowner_guide_long.pdf
http://pubs.ext.vt.edu/448/448-407/448-407.pdf
38
Brian Benham
Extension Specialist
Website:
www.wellwater.bse.vt.edu
Email: benham@vt.edu
Ph: 540-231-5705
39