Everything that goes down a household drain flows into the tank via the inlet pipe.
There are three layers of material in a septic tank.
a. Lighter fats and grease float on the top layer (scum).
b. Heavier solid wastes sink to the bottom of the tank (sludge).
c. The middle layer is effluent (liquid waste).
Bacteria in the tank converts the scum (fats and grease) into effluent. If your septic tank is healthy, the bacteria work to keep the sludge level low. High water usage, antibacterial cleaners, bleach, excessive garbage disposal waste, medications, grease, antifreeze, painting products, hot tub water and pesticides will kill or swamp the good bacteria.
The effluent (liquid waste) flows out to the drain field.
The sludge layer needs to be periodically pumped out.
Your pumping schedule
The Septic Tank
What is it?
According to Webster's Dictionary, the septic tank is "an underground tank in which waste matter is putrefired and decomposed through bacterial action." The tank is a watertight container which is most commonly made of concrete. It may also be made of fiberglass or polyethylene. Whatever you flush or pour down the drain in your home goes into the septic tank.
All septic tanks should have an inlet (from the house) and an outlet (to the drain field or other treatment area), risers to provide access to examine the PVC pipes and baffles and a manhole for pumping out the tank.