A. Septic tanks shall be installed on a solid, level base, with access hole covers 6 inches to 12 inches below the finished grade. If the cover is airtight, equipped with a hasp, and kept locked to prevent unauthorized access, the cover may be shallower or above grade. The tank shall be installed at a depth that provides adequate gravity flow from the building or facility sewer that meets the requirements of the South Dakota State Plumbing Code, ARSD § 20:54:11:09;

B. The tank shall be installed on undisturbed soil. If over-excavation occurs, it shall be backfilled with sand to the correct elevation and compacted. Backfilling around the tank shall be accomplished in a manner to prevent settlement, and to prevent undue stresses on the tank and to the inlet and outlet pipes;

C. When multiple tanks are used to obtain the required liquid volume capacity, the tanks shall be connected in series. The interconnecting pipes between tanks shall be at least 6 feet in length and unperforated. No more than 4 tanks in series are permitted to obtain the required liquid volume capacity. The first tank shall not be smaller than any of the subsequent tanks in the series;

D. All tanks shall be located in an area accessible for the pumping of their contents. There shall be no constructed building or facility of any kind covering any of the tanks;

E. Flotation collars shall be used in areas with high ground water potential;

F. The inlet and outlet pipes shall be made watertight by grouting with cement or corrosion-resistant sealants. The pipes shall be supported on the outside of the tank to prevent failures due to settling. The pipes connecting septic tanks installed in series shall be Schedule 40 PVC soil pipe of 4-inch minimum diameter; and

G. During installation, any damage to the watertight coating or interior of a tank shall be repaired and tested by filling with water.