Minnesota Administrative Rules
Agency 167 - Pollution Control Agency
Chapter 7080 - INDIVIDUAL SUBSURFACE SEWAGE TREATMENT SYSTEMS
Part 7080.1920 - SEPTIC TANK DESIGN

A. have a liquid depth of at least 30 inches. Any liquid depth that is greater than 84 inches must not be used when calculating the septic tank liquid capacity;

B. have a minimum of six feet between the inlet and outlet of the tank, rather than between compartments, or have a minimum of six feet from the inlet of the first tank to the outlet of the last tank in series;

C. if site conditions warrant, the inlet and outlet are allowed to be located on walls that are not opposite each other along the axis of maximum dimension; however, the requirements of item B must be met;

D. have an inlet invert at least two inches above the outlet invert; and

E. have a space between the liquid surface and the top of the inlet and outlet baffles of not less than six inches or 100 gallons, whichever is greater, for all liquid depths with an effluent screen and alarm or for liquid depths of less than 39 inches without an effluent screen and alarm. The space between the liquid surface and the top of the inlet and outlet baffles must not be less than eight inches for liquid depths of 39 inches or more without an effluent screen and alarm.

In addition, there must be at least one inch between the underside of the top of the tank and the highest point of the inlet and outlet baffles.