Essentially, a septic system is made up of sewer lines, a septic tank, and a drain field. The sewer lines transport sewage from the drains into the septic tank, where solid waste breaks down naturally over time. As it breaks down, waste settles at the bottom of the tank. Liquid waste remains at the top of the tank and is sent to the drain field via an electric pump or the force of gravity. When liquid waste arrives at the drain field, it is distributed into the ground, where the soil naturally filters and absorbs it.