Private septic systems are a natural, cost-effective and environmentally friendly means of wastewater treatment and are often found in rural areas characterized by large plots of land upon which are widely spaced houses. Thus, they are more economical and less destructive of the environment than centralized systems that require miles of sewer lines. As private systems, they are self-contained and distinct from municipal sewer systems.
Septic systems are used to treat household wastewater that originates in toilets, kitchens and laundry rooms. Water that does not contain human waste is known as “gray water” and comes from dishwashers, bathtubs, showers and laundry appliances.
There are two types of septic systems: aerobic and anaerobic. Aerobic treatment units are suitable for small lots where there is insufficient room for a drain field. These systems require electricity and more frequent septic tank emptying than conventional anaerobic systems.
In the most common and basic anaerobic configuration, no electricity is required. Septic systems funnel household wastewater via the sewer pipe to an underground septic tank, which is outside the house. Septic tanks are watertight boxes that may be constructed of plastic, polyethylene, concrete, fiberglass or steel, steel being the least durable of the materials. The tank allows the natural separation of solids and liquids. From the tank, liquid flows to the drain field, aka leach field, soil disposal field or soil absorption field, which is a shallow excavation made in unsaturated soil. A drain field is a series of trenches or a gravel- or sand-lined bed; it is one to three feet below ground and contains perforated pipes or drain tiles. The wastewater is treated as it slowly trickles from the pipes into the ground and down through the soil and gravel, which are the biological filters. The wastewater, having percolated through the soil, is then discharged to groundwater. The soil naturally removes nutrients, viruses and harmful coliform bacteria (an indicator of human fecal contamination).
In the septic tank, organic matter is digested by anaerobic bacteria and solids, and floatable matter such as oils and grease are separated from the wastewater. Liquid, known as effluent, emerges from the tank into perforated pipes that are in the underground leach field, leaching chambers or similar devices that will slowly release the treated effluent into the soil or surface water. Other systems employ gravity or pumps to direct the effluent through sand or other organic matter to remove or neutralize pollutants and other contaminants. Some systems evaporate or disinfect wastewater prior to discharge into the soil or surface water.
Septic tanks hold the wastewater long enough for the solids and liquids to separate into three layers. Solids fall to the bottom, forming sludge; oils and grease rise to the top as scum; the middle layer consists of partially clarified wastewater. Both sludge and scum are prevented from exiting the tank by the tank’s compartmentalized construction. Sludge and scum remain in the tank where bacteria contained in the wastewater break down the solids; solids that cannot be broken down remain in the tank to be pumped out at a later date. The clarified liquid flows to the drain field.
If you are buying property upon which you suspect that there is a septic system, here are some clues: The property tax bill contains no municipal sewer charge, there is a private well, there is an unmetered water line entering the house and neighbors have septic systems. Look near the house for a lid or manhole cover. Check the house’s blueprints.
Properly cared for, basic private septic systems have their virtues. A passive system does not require external energy and mechanical components in order to function. There is no municipal sewer charge. However, there is the minor cost of having the tank pumped out every year or two. Low-Pressure Dose Systems require a pump to move effluent to a drain field; conventional systems that don’t percolate well will require frequent pumping. (Percolation rate refers to the soil’s ability to absorb water.)
Normally, maintaining a septic system involves a dose of common sense. Don’t drive over the drain field or plant trees or shrubs near it to prevent roots from entering the lines and plugging them. Allow grass, not concrete or other materials, to cover the drain field. Divert surface water runoffs, such as from roofs, away from the drain field. To avoid destroying or overtaxing the biological digestion process and to avoid clogging pipes and pumps, do not flush down the drains or toilets coffee grounds, dental floss, sanitary napkins, tampons, hair, disposable diapers, kitty litter, cigarette butts, bandages, fat, grease, oil, paper towels and the like. Never flush chemical contaminants such as paints, varnishes, thinners and pesticides that could contaminate surface and groundwater.
Watch for system malfunctions such as bright green, spongy grass even in the absence of rainy weather, wastewater backing up into the house including pooling water or muddy soil in the basement and around the septic system and foul odors around the drain field and septic tank. If you notice any or all of these signs, call a professional to pump out your tank.
Properly constructed and maintained, your septic system can happily co-exist with you. My family has done it since 1941!
By Vivian J. Oleen
Vivian Oleen is an associate broker with Sopher Realty.