A septic system consists of two main parts-a septic tank and a drainfield:
The septic tank is a watertight container, usually made of concrete or fiberglass, with an inlet and outlet pipe. Wastewater flows from the home to the septic tank, where it remains until the liquids and solids separate after being broke down by a naturally occurring bacteria. Three layers will form inside the tank; a scum layer where solids less dense than water (grease, oils, etc.) float on top, a sludge layer where solid waste with a higher density than water settles, and the middle layer with partially clarified wastewater. The scum and sludge layers are where the bacteria can be found and where the wastewater breakdown occurs. The tank needs to be pumped when scum and sludge that cannot be broken down is present. The clarified liquid flows from the septic tank to the drainfield.