A typical septic system consists of a septic tank and a drainfield (or soil absorption field). The septic tank digests organic matter and separates floatable matter (e.g., oils and grease) and solids from the wastewater.

The septic system consists of three components (Figure 1): the tank, the drain lines or discharge lines, and the soil treatment area (sometimes called a drainfield or leach field). Tank sizes vary depending on the size of the building.

A typical system consists of a waste pipe from the house, a large concrete, fiberglass, or plastic septic tank, and a leach field. The most common type of leach field consists of a series of perforated distribution pipes, each set in a gravel-filled absorption trench.