DWM Publications > Table of Contents > Chapter Eight

THE CLEAN WATER BOOK:
CHOICES FOR WATERSHED PROTECTION

A key problem with septic systems is a misunderstanding of their function and purpose. Septic systems are designed for the treatment of sanitary waste. They are not intended for the disposal of household waste or other chemicals. Proper maintenance is crucial in keeping a septic system working.

Septic tanks can be constructed of concrete, fiberglass or polyethylene, and must be large enough to hold one day's flow of waste water from your home. Solids settle to the bottom. Light materials float on the surface and only the wastewater filters out into the drain field. The subsurface disposal area generally consists of a distribution box and perforated distribution lines installed in subsurface gravel-filled beds or trenches. The subsurface disposal area receives wastewater from the septic tank and removes harmful, disease causing microorganisms, organic chemicals and nutrients. Treatment of sanitary waste in the septic system is a function of bacteria/viral die-off. For this part of the system to function properly, it must be constructed carefully on suitable soil.

The soil also needs time to filter out these harmful materials from the wastewater. "Suitable soils" do not include coarse sand (which permit wastewater to pass through too fast) or pure clay (which accepts only small amounts of wastewater). State and local regulations that determine what constitutes suitable soil have been developed after careful consideration of many factors that affect a soil's ability to adequately treat domestic wastewater. Before a septic system is built, State laws require that a "perk" (percolation) test be performed to determine how fast the soil absorbs water. Soil examination by a

professional soil scientist can provide a more reliable assessment of the capacity of the soil to accept wastewater. When designing a system, your design engineer should check the water table level to be sure it is at least four feet below the bottom of the subsurface disposal area. The drain field, or absorption system, is critical to how well your septic system functions. Perforated pipes must be laid in suitable soil, away from tree roots and manmade structures. The drain field must be a large enough area to absorb your home's daily wastewater.

If the septic system is not functioning properly, it can also release disease-causing microorganisms. The principal signs of septic system problems are easy to detect: effluent rising to the ground or drains and toilets that operate sluggishly or not at all. Septic system problems can be minimized by understanding the needs of your system and observing several precautions.

Toxic and household hazardous chemicals should never be disposed of through your septic system, as these can disrupt its functioning and contaminate ground water. Such chemicals include paints, varnishes, pesticides, solvents and drain openers. See the Household Hazardous Waste chapter in this booklet on proper disposal of these chemicals.

There is no known substance capable of eliminating or reducing the build-up of sludge and scum that makes periodic cleaning necessary. Do not put chemicals in your septic system for treatment or maintenance.

Motor oil from your car or truck should be recycled by taking it to your nearest recycling center or a service station. Motor oil should not be disposed of in a septic system.

Inert or non-biodegradable materials also should not be disposed of through your septic system. Examples are cat box litter, disposable diapers, coffee grounds, sanitary napkins and paper towels. These items quickly fill your septic tank, decrease its efficiency and will require more frequent pumping of your tank.

Large quantities of cooking grease, oil and fats should not be allowed into septic systems. These can contribute to blockage within the system. The use of garbage disposal units should be avoided, as these increase the amount of solids in the septic system, requiring more frequent pumping.

The performance of your septic system will be improved if you cut down on water use so that a smaller volume of wastewater passes through the system. Water-saving shower heads can be easily installed and may reduce both your water use and heating bill. Be careful to turn taps off when not in use and repair or replace leaking faucets. Your subsurface disposal area will not work well if there is too much water in the soil. Water drained from basement floors, footings or roofs should be directed away from the disposal area to some other area in your yard. Your yard surface should be graded so that stormwater drains away from the septic drainage field and not toward it.

In addition to monitoring what goes into your system, you will also need to inspect and pump out your system on a routine basis. Systems should be inspected once a year and should be pumped out every two to three years on the average. CAUTION: Toxic gas, can accumulate in septic systems, so use extreme care when opening your septic tank. A final source of septic system malfunctions are problems that occur during construction. These include soil compacting due to excavation at times when soil moisture is high, pipes laid on improper grades, incorrect joints and alignments between system components and pipes broken or crushed during the building process.

Direct water from down spouts and roof, footing and basement drainage away from the disposal field.

Dispose of hazardous household chemicals properly. Do not pour them down the toilet or drain. They can destroy the bacteria in the septic system and contaminate local ground water.

Don't use garbage disposals. They contribute unnecessary solids and grease to your septic system.

Conserve water whenever and wherever possible.

Don't use toilets as trash cans. Dispose of solid waste in your garbage.

Monitor your septic tank yearly and have a reputable contractor remove sludge and scum every two to three years. (This helps ensure that there is enough space in the tank for wastewater and prevents solids from escaping into the absorption system.)