Most residential septic tanks are fairly shallow in the ground, but depth varies by site and local code.
Typical burial depth
In many areas, septic tanks are buried with the top of the tank roughly 4 inches to 4 feet below the ground surface. The lid is often about 6–12 inches below grade so it can be accessed for pumping and inspection.
Factors that change depth
Depth is set mainly by:
- Local building and health regulations, which may specify minimum soil cover and maximum burial depth for access and protection from freezing.
- Site conditions such as frost line, soil type, groundwater level, and the elevation of the house sewer line, all of which affect how deep the tank and drain lines can be placed.