All the wastewater from a house gets pumped into a septic tank, which is stored underground. The wastewater then separates into solid sludge and scum, according to the Environmental Protection Agency (EPA) Homeowner's Guide to Septic Systems.
A septic system's only function is to partially treat household wastewater before releasing it into nearby fields, which then complete the wastewater treatment cycle.
A properly functioning septic tank removes pollution from household water, such as bacteria and nitrogen, which can contaminate the local environment and spread disease.
The last part of the septic tank treatment system can push too much wastewater into the drainage field and overflow into the ground or clog plumbing, according to the EPA.
To keep a septic tank functioning properly, the EPA advises that homeowners have their septic tanks inspected every three years and then pumped once every three to five years, with greater frequency when more people live in a house.