The inlet and outlet in these tanks are located near the top of the units. Both the inlet and outlet are covered with a baffle that extends down to the effluent. these baffles help reduce solids output. Most solids will settle on the bottom of the tank. Then solids are then partially consumed by anaerobic bacteria. Remaining solids are removed by pumping.

Greases, oils and suspended solids (solids held suspended in the waste water) form a scum layer at the top of the tank. This layer is held in the tank by the baffle over the outlet of the tank. In the center of the tank a clear layer of effluent forms. The outlet baffle is placed so that discharge from the tank comes from this clear layer. Most studies indicate that septic tanks will remove about 50% of the solids that flow into it. This varies from system to system based on total flow during the day, and total rest time during the day.

Assuming an average flow system, one tank will remove 50% of the solids, a two tank system will remove 75% of total solids, etc. There are also a number of filters that can be installed in a tank to reduce solid output. See Zabel Filters. Another aid in reducing solid output is multiple chamber tanks. These are septic tanks having more than one chamber. Lake Shore offers several tanks with this configuration. See the 1200 Gallon, 1000/750 Gallon, 1200/1000 Gallon two compartment tanks.

Tanks should be pumped every two years. Current research indicates that this frequency is optimal. Pumping more often results in reduced bacterial action. Pumping less frequently will result in smaller solid settling distance and higher solids output. Any filters installed in a tank must also be cleaned regularly. See manufacturers recommendation for proper cleaning schedule.

Specific dimensions and cited requirements refer to Wisconsin Administrative Code ILHR83. This is not to imply that this website has been reviewed, approved, or recognized by any regulatory agency.