Septic Systems — How Do They Work? How Do You Maintain Them?
Illustration adapted from
Septic Systems www.cdc.gov
Failed or improperly functioning
private residential septic systems
threaten nearby water bodies.
When a septic system is not work-
ing properly, untreated waste water
can enter the lake, directly or almost
directly. Though a septic system is
designed to eventually return “clean”
waste water to the ground water the Leach Field
waste must first go through the whole
process of bacterial action and passage
through appropriate materials that
Untreated Waste Can Be Your Septic System
Harmful to Health
Waste from a home that has not Dirty water leaving your house – D Box
passed through a functioning septic laundry, kitchen, bathroom – ends up When wastewater enters the tank, a
system can carry bacteria into the wa- somewhere. But where? And how compensatory volume of the liquid
ter body. The presence of E. coli bac- does it get treated before it ends up layer in the septic tank passes on to
teria demonstrate the presence of fecal back in the water cycle? If you are the other end, past a baffle which
material in the water. E. coli are seen connected to a sewer, municipal sew- holds back solids, into a pipe that
as a marker; when they are in the wa- age treatment plants process the waste empties in a distribution or diversion
ter, other health hazards (bacteria or and the treated liquid is usually re- box (D box). The D box has multiple
viruses) associated with human or ani- leased back into rivers or larger exits, and from it the water passes into
mal waste may be present. (While not streams. But if you have your own a number of perforated pipes. From
prevalent in the US, diseases such as residence septic system, how does it these pipes, it disperses into the mate-
cholera and typhus are water-borne.) work? rial of the leach field or bed. Waste-
Nutrients Harmful to Lakes Septic Tank water can flow by gravity or be
Untreated residential waste water is All wastewater leaving your house pumped between the different parts of
also heavy with nutrients that feed goes out an underground pipe and the system.
unwanted plant and algae growth in dumps into your septic tank, a large Leach Field
the lake or pond. Algae blooms and cement or plastic chamber. Here, the A typical leach field is made up of
thriving invasive plants can be sup- solids settle to the bottom, and a layer layers of sand and/or gravel that allow
ported by nutrients from septic sys- of scum made up of soaps, grease and the waste water to pass through at an
tems that are not working well. other lighter-than-water elements appropriate rate and into the soil be-
Untreated septic waste can also floats on the top. All effluent contains low. Septic system design relies on
contain chemicals that are harmful to bacteria, and there are anaerobic bac- permeable soils which will filter the
plants, aquatic life and humans, such teria (that do not need oxygen to waste water or effluent as it passes
as chlorines and various chemicals and work) in the sludge layer in the tank. through, so when a leach field is con-
hormones used in pharmaceutical and These bacteria go to work decompos- structed, stone, permeable gravel and
personal care products. Some of these ing the solid materials and reducing other suitable materials are brought in
are altered or removed as the waste them to sludge which remains in the to construct the bed, and regulations
passes through the microbial and fil- septic tank. The layer above the require adequate depth of good per-
tration action of a septic system, but sludge and beneath the scum is a liq- meable soil where the leach field is
reach the lake water when the system uid layer with dissolved or suspended
waste. Please turn over — continued on back
is not working properly.
A reprint from the LSPA newsletter, the Beacon, April 2007. More info: 763-2210
Continued from opposite side Septic System Maintenance
made. A properly designed and installed drain or toilet – they can kill the bacte-
Back into the Groundwater septic system, sized for the use it will ria needed to break down solid waste.
The process of filtering or perco- get (number of people, whether there “Chemicals” include pesticides, sol-
lating through the soil cleanses the is a garbage disposal) will function vents, oils, medicines, caustic house-
wastewater. Dissolved waste and bac- well throughout its 20-30 year life hold cleaners, etc. They can also pass
teria cling to soil particles or are eaten span if it is maintained and treated through and into the soil, then the
by microorganisms that require oxy- well. Maintenance is inexpensive; re- ground water, with the water leaving
gen for the process. Eventually the placement can be very costly. the leach field – and end up in well or
resulting “clean” water becomes part When the use of a house increases, lake waters.
of the underground water systems, or the septic system must be enlarged to • Do not use a garbage disposal, par-
ground water. function properly. If you add bed- ticularly if it was not included in the
rooms, pack the house with guests on original design of your system. (They
the weekends, or change from sea- require significantly larger tanks and
sonal to year-round use, you are out of leach fields.)
balance with your septic system de-
sign. You may need to replace your • Do not use additives sold to “extend
system because of failure sooner than septic system life” — They are not
its original design lifetime. necessary and may be harmful.
Pump Out Regularly For Your Leach Field
The most important thing is to • Do not drive or take heavy machin-
have your septic tank pumped regu- ery across it. (The weight can com-
larly, to remove accumulated sludge pact the soil, inhibiting filtration, as
and scum before it begins to clog your well as break the pipes).
leach field. The usual recommended
A septic tank, with its three layers of sludge interval is every two to three years. • Keep trees from growing on or near
at the bottom, liquid waste in the middle, it (their roots can clog or break up the
and scum and grease at the top. The company that pumps your tank
can keep you posted on the condition pipes).
Illustration adapted from www.cdc.gov of the tank and whether you are • Direct runoff away from the leach
pumping frequently enough. If you field area so it doesn’t over saturate
use a garbage disposal you must pump the soil.
A reprint from much more frequently.
Other Things To Do To Extend Baffle or Tank Replacement
the LSPA newsletter, the Life of Your System: If you have an old metal septic
• Conserve water – so the soil tank it should be replaced as it will
the Beacon, around the leach field does not be- deteriorate and let waste pass directly
April 2007. come too saturated. Use low flow into the soil. You can replace a tank
fixtures, fix leaks. Spread out heavy without replacing an entire septic sys-
More info: LSPA, 763-2210 tem. Your septic tank pumper can tell
water loads through the day and week
(don’t do all laundry in the same day, you if your tanks’ baffles are in good
or when people are showering). shape: if not, they can be replaced.
• Do not flush bulky items like dispos- Septic systems that are well main-
able diapers, sanitary pads or paper tained can last 20 or 30 years, but
towels. eventually will need replacing. Newer
• Do not pour fats or greases down systems have new, better technology
the drain – they can clog the leach than old ones, and often include
• Do not put chemicals down the