Most septic systems for homes are underground and covered. A septic system typically consists of three components: a household wastewater pipe, a septic tank and a drain field.
The household wastewater pipe carries water into the septic system every time someone flushes a toilet or turns on a faucet. The water usage habits for a given home, in addition to the number of people living in it, determine the amount of flow going into the septic system. If the amount of wastewater exceeds the system's capacity, an overload occurs, leading to high maintenance costs.
House size and state or local regulations determine the size of the septic tank. An ideal gauge for house size is the number of bedrooms in the home. Solid material typically sinks in the septic tank, while fats and grease float. The liquid effluent between the materials flows out to the drain field through a T-shaped outlet. Some tanks have risers that enable easy access to check sludge levels.
At the drain field, liquid effluent is distributed into a succession of trenches lined with gravel and covered with soil. The soil is loaded with bacteria to purify waste before it gets into groundwater. Given that most septic systems are underground, they are often ignored until they fail. Understanding the features of the system is a fundamental part of caring for it.