The waste from your building enters the first chamber of a septic tank, most of the septic tank will be filled with effluent (watery waste). The bacteria will break down the solid waste and this sludge will settle to the bottom of the septic tank. The septic tank is a sort of settling pond and heavier solids sink to the bottom and a filter inhibits most solids from entering the outlet pipe. The effluent then crosses over into the pump chamber where it flows to the septic drain field a large area designed to allow the gravel and soil to decompose organic waste.