Conventional In-Ground Septic System
In a conventional septic system, gravity carries wastewater from the house into the septic tank and then to the drainfield. The septic tank is a watertight vault usually made of concrete, polyethylene, or fiberglass. Wastewater settles there long enough to separate.
The greases and oils that rise to the top as scum and the solids that sink to the bottom as sludge both get removed by a septic pumping company every few years and carted to an approved disposal site.
The relatively clear water in the middle flows out to the drainfield. This area, which must be kept free of trees and shrubs so their roots don’t damage it, consists of plastic chambers buried in trenches in approved soil below the surface. As water trickles out of the pipes, the soil and its microbes act as natural filters to clean the water.