Waste flows first to a septic tank. The solids settle and scum is held at the top of the tank by baffles. Liquid flows to the second part, the drain field. Bacteria in the septic tank convert part of the solids to liquid, which then flows on to the drain field. The drain field is a system of perforated piping that allows wastewater to seep into the ground.
Proper design is important for a septic system.
Minimum tank capacity is based on the number of bedrooms and the maximum number of people served. The size of the drain field or the length of the drain field trenches must be able to handle the water generated by the household. Soil conditions at the home site are very important in designing the system. A percolation test determines the soil permeability, a measure of the potential for water movement through the soil. A septic system may develop operative or maintenance problems for several reasons.