Septic Systems - The Basics
Septic systems are required when there are no community sewers available to dispose of your home’s wastewater. The rules for septic systems vary greatly from community to community, so contact your local officials to get details.
Septic systems are relatively simple, and very efficient. Human waste from toilets, and gray water from baths, showers, sinks and laundry are gravity fed from your home via a large drainpipe, typically 4" in diameter, to a large holding tank. This concrete, steel or plastic tank, holding 1000 gallons or more, is typically buried 1 to 3 feet underground and located approximately 10 feet from your dwelling.
Once in the tank, the waste separates into layers, a sludge layer at the bottom, a liquid layer in the middle, and a scum layer on the top. Bacteria process the sludge layer and produce methane and hydrogen sulfide gases which vent through the other layers. The tank is designed with baffles or chambers, which allow the liquid layer, called affluent, to exit, but retain the scum and sludge layers within.
The affluent is piped to a network of perforated pipe or clay tile buried 4 to 6 feet below grade in a layered bed of gravel and soil called an absorption field or leaching bed where the affluent is absorbed and safely dissipates. This network can be several hundred square feet and is normally covered with a soil barrier, then sand, then another soil barrier, and finally topsoil and grass. Each of these components is an important part of the system.
A properly designed and maintained septic system will safely treat your wastewater for 30 to 50 years.
Note that eave trough drainage, pool drainage, sump pumps, sidewalk and road run-off should never be drained into your septic system. Water softener backwash is not septic and can be drained to an area other than the septic system. However, less than a 100 gallons a week of water softener backwash may be drained into your septic system. Rather than using kitchen garbage disposal unit which drains into your septic system, consider installing a composter in your backyard.
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