A typical household sewage treatment system consists of a house sewer, septic tank, distribution box and absorption field or seepage pit.
House Sewer - The pipeline connecting the house and drain and the septic tank.
Septic Tank - Untreated liquid household wastes (sewage) will quickly clog your absorption field if not properly treated. The septic tank provides this needed treatment. When sewage enters the septic tank, the heavy solids settle to the bottom of the tank; the lighter solids, fats and greases partially decompose and rise to the surface and form a layer of scum. The solids that have settled to the bottom are attacked by bacteria and form sludge. Septic tanks do not remove bacteria and, therefore, what is discharged cannot be considered safe.
Distribution Box - Serves to distribute the flow from the septic tank evenly to the absorption field or seepage pits. It is important that each trench or pit receive an equal
amount of flow. This prevents overloading of one part of the system.
Absorption Field - A system of narrow trenches partially filled with a bed of washed gravel or crushed stone into which perforated or open joint pipe is placed. The discharge from the septic tank is distributed through these pipes into trenches and surrounding soil. The subsurface absorption field must be properly sized and constructed. While seepage pits normally require less land area to install, they should be used only where absorption fields are not suitable and well-water supplies are not endangered.
Cesspools - Work in a similar manner to septic systems. Sewage water usually seeps through the open bottom and portholes in the sides of the walls. These can also clog up with overuse and the introduction of detergents and other material which slow up the bacterial action.
When the sewage backup occurs, homeowners usually have the system pumped out. Pumping out will only relieve the system temporarily. The clogged pores in the ground remain and eventually the system will have to be pumped again and again.