A septic system has two main components: the septic tank
and the drainfield.

Septic Tank
The size of the septic tank varies based on the number of bedrooms in the home, the number of wastewater
contributing fixtures and appliances (i.e. whirlpool bath, garbage disposal, dish/clothes washer, etc.), and/or state and local regulations. Waste enters the tank from household plumbing through a pipe and enters the septic tank, which is a buried watertight container made of materials such as concrete, fiberglass, or plastic. The tank holds the waste long enough to allow solids and liquids to separate and form three layers:
• Scum layer – solids lighter than water, such as greases or oils, float to the top
• Liquid layer – partially clarified wastewater
• Sludge – solids heavier than water settle at the bottom of the tank

The tank also contains baffles and tees, which slow the wastewater entering the tank to allow solids to easily
settle out.

Treatment of the wastewater begins in the septic tank as naturally-occurring bacteria in the sewage work to break down the organic matter in the tank. Sludge and scum that cannot be broken down remain in the tank until it is pumped. The partially clarified liquid layer then flows through an effluent filter out of the tank and into the drainfield for final treatment.

Drainfield
The wastewater (effluent) entering the drainfield may contain many potentially harmful microorganisms and
pollutants, many of which can be effectively removed through soil treatment. The drainfield, also referred to as a leachfield, disposal field, or soil absorption system, consists of perforated pipes or chambers within a series of trenches or mounds lined with gravel and buried one to three feet below the surface. Water flows through the perforated pipes or chambers and slowly trickles through the gravel and into the surrounding soil, where the natural processes in the soil complete the sewage treatment process.