Water Resources Center

The Water Resources Center is affiliated with the College of Food, Agricultural and Natural Resource Sciences and University of Minnesota Extension.

Gravity Distribution Systems

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Gravity distribution of septic tank effluent has been the most common design over the history of in MN treatment in MN. Less expensive to install and maintain than systems in which effluent is pumped, gravity distribution systems take advantage of natural elevation differences. Effluent flows down from its sources to the septic tank, then on to the soil treatment system as shown in Figure 11.10 in the SSTS Manual for Septic System Professionals in Minnesota.

Today, gravity distribution systems for conveying septic tank effluent are used in two types
of systems: either trench or seepage bed systems.

There are several types of gravity distribution devices that receive and transfer effluent from the supply pipes to distribution pipes or down slope components : drop boxes, distribution boxes, valve boxes, and manifolds. The primary purpose of flow distribution devices is to control the flow of the effluent into the drainfield.

Click here for more general information on gravity distribution systems (.pdf)

Distribution box
Drop box