The septic tank is the first part of your septic system when the pipe leaves your house. All waste water from the shower sinks and toilets exits through a pipe right into the septic tank. Septic tanks are normally made from cement just like your foundation of your home. A simple box shape it has one pipe entering from your house and another pipe exits to the distribution box. The pipes normally are pvc, but some older homes have clay or metal pipes. Here in the septic tank good bacteria begins to break down up to 50% of the solids into liquid and gas. The overflow pipe, the exit is located high up from the bottom of the tank so that only liquid waste will exit. keeping the solid material at the bottom for biodegrading.