Septic drain fields, also called
leach fields or
leach drains are used to remove contaminants and impurities from the liquid that emerges from the
septic tank. A
septic tank, the septic drain field, and the associated piping compose a complete
septic system. The septic drain field is effective for disposal of organic materials readily
catabolized by a microbial
ecosystem. The drain field typically consists of an arrangement of trenches containing perforated pipes and porous material (often
gravel) covered by a layer of
soil to prevent
animals and
surface runoff from reaching the
wastewater distributed within those trenches. Primary design considerations are hydraulic for the volume of wastewater requiring disposal and catabolic for the long-term
biochemical oxygen demand of that wastewater.