Gravity-Flow System

• The gravity-flow septic system consists of a buried septic tank or tanks and a distribution system. The septic tanks hold wastewaters and solids before they're broken down and arrive at the distribution system.
  
  

Distribution System Function

• The distribution system is an underground drain field. It may be a trench filled with gravel, buried plastic receptacles or plastic pipes. Whichever material is used is meant to hold wastewater from the septic tank while it seeps into the surrounding soil.
  
  

The Soil's Function

• As the wastewater seeps into the ground, it is filtered by the soil, which removes organic matter and minute solids. Then bacteria in the soil dissolve the minute solids.
  
  

Maintenance

• Maintenance for a gravity-flow septic system amounts to pumping out the septic tanks every two or three years. How often you pump out the tanks depends on their size and how many people live in the house.