The wastewater coming out of the house enters the septic tank through discharge sewer pipe and after going through the inlet baffle, the solid materials get separated from liquid. Few solids may settle on the tank bottom; however, rest of the elements keep on flowing in the scum layer. The solids get decomposed with bacterial action. In simple terms, septic tanks have three parts: Sludge layer on the bottom, liquid zone in the middle and floating scum layer on the top portion. The inlet and outlet valves maintain the flow of liquid in specific direction.