Home septic systems have two main components: a septic tank where solid waste is stored and an absorption area where waste water is treated. The waste drains from the house drain into the septic tank and separates out into three layers.
1.
Solids settle to the bottom and decompose to form the bottom sludge.
2.
Greases and Oils (lighter than water) form a floating surface layer of scum.
3.
The remaining wastewater, after the separation of sludge and scum, make up the middle later.
The wastewater leaves the septic tank and travels through a baffles. These baffles ensure the wastewater is relatively free of scum and sludge. The water travels to the drain field (gravel-filled trenches) to treat the wastewater. The soil acts as a biological and physical filter to remove harmful substances.
Septic tanks must be routinely pumped to remove the accumulation of the bottom sludge and surface scum. If the tank is not pumped regularly to remove these solids, then the tank will fill with sludge and scum. When this happens, the solids will be washed out to the drain field, where they will quickly clog the soil and eventually lead to system failure.