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31 INDIVIDUAL SUBSURFACE SEWAGE TREATMENT SYSTEMS 7080.1930 <br />7080.1920 SEPTIC TANK DESIGN. <br />Septic tanks must: <br />A. have a liquid depth of at least 30 inches. Any liquid depth that is greater than 84 inches <br />must not be used when calculating the septic tank liquid capacity; <br />B. have a minimum of six feet between the inlet and outlet of the tank, rather than between <br />compartments, or have a minimum of six feet from the inlet of the first tank to the outlet of the last tank in <br />series; <br />C. if site conditions warrant, the inlet and outlet are allowed to be located on walls that are not <br />opposite each other along the axis of maximum dimension; however, the requirements of item B must be <br />met; <br />D. have an inlet invert at least two inches above the outlet invert; and <br />E. have a space between the liquid surface and the top of the inlet and outlet baffles of not less <br />than six inches or 100 gallons, whichever is greater, for all liquid depths with an effluent screen and alarm or <br />for liquid depths of less than 39 inches without an effluent screen and alarm. The space between the liquid <br />surface and the top of the inlet and outlet baffles must not be less than eight inches for liquid depths of 39 <br />inches or more without an effluent screen and alarm. <br />In addition, there must be at least one inch between the underside of the top of the tank and the highest <br />point of the inlet and outlet baffles. <br />Statutory Authority: MS s 115.03; 115.55 <br />History: 32 SR 1347; 35 SR 1353 <br />Published Electronically: October 10, 2013 <br />7080.1930 SEPTIC TANK CAPACITY. <br />Subpart 1. Dwellings. The liquid capacity of septic tanks must be at least as large as the liquid <br />capacities given in Table V. <br />Number of bedrooms <br />3 or less <br />4 or 5 <br />6 or 7 <br />8 or 9 <br />TABLE V <br />Septic tank liquid minimum capacities (gallons) <br />1,000 <br />1,500 <br />2,000 <br />2,500 <br />Where more than nine bedrooms are present, the septic tank capacity must be calculated by the <br />following formula: 2,500 + ([# of bedrooms - 9] x 250). <br />Subp. 2. Garbage disposals. If a garbage disposal unit is anticipated or installed in a dwelling, the <br />septic tank capacity must be at least 50 percent greater than that required in subpart 1 and must include either <br />multiple compartments or multiple tanks. In addition, an effluent screening device is recommended. <br />Copyright ©2014 by the Rev <br />so <br />of Statutes, State of Minnesota. All Rights Reserved. <br />