All sewage tanks must be watertight, including at all tank and riser joints, riser connections, and pipe connections.
An assessment of all models of sewage tanks to be used must be conducted to determine:
the structural integrity of the tank design; and
the adequacy of the manufacturing process of watertightness.
Sewage tanks, including riser joints, riser connections, and pipe connections must be designed, manufactured, and installed to be watertight under normal use.
The structural integrity of each model of tank manufactured and all poured-in-place tanks must be verified by calculation, proof testing, or a licensed professional engineer to determine the horizontal and vertical loads that the tank can withstand when empty. Tanks must be reverified for structural integrity if the design, materials, or construction methods are modified. A licensed professional engineer shall certify in writing if different manufactured models are similar enough so that the structural integrity information for one model is valid for other models. Verifications must be submitted to the commissioner. The commissioner shall maintain and make available the verifications upon request.
At least one tank per year, per model must be tested for watertightness. All poured-in-place tanks shall be tested for watertightness. Records of testing must be maintained by the manufacturer for three years and must be available to the commissioner and local unit of government if requested. Tanks must be tested and meet or exceed the applicable requirements of subitem (1), (2), or (3):
when empty, a tank must maintain a vacuum of at least two inches of mercury for five minutes, without loss of pressure;
concrete tanks must hold water for one hour, without loss, after the tank has been filled with water to the top of the tank, let stand for 24 hours, and then refilled to the same level; or
fiberglass-reinforced polyester or polyethylene sewage tanks must hold water without loss for one hour after being filled.
Sewage tanks that do not pass the tests listed in item A must not be used until repaired and retested. The repair and retest procedure must be repeated until the tank passes the test or the tank must not be used.
October 10, 2013
Copyright © 2013 by the Revisor of Statutes, State of Minnesota. All rights reserved.