Abstract: A corrugated plastic side wall (A) extends from a bottom area (14) to an apex area (12). A riser (B) extends from the apex area above the ground level. A ring of steel channel (10) is fastened around the apex area to prevent the apex area from becoming distorted when the soil in which the tank is buried becomes water-laden. A tank bottom wall (122) is domed inward to inhibit exterior hydraulic pressure from flexing the bottom inward and from urging the corrugated side walls adjacent the bottom to compress to a smaller diameter in an accordion-like fashion. Downward projecting can (124) and boxes (126) extend from the domed bottom surface to a flat plane to prevent the dome from flexing outward under the weight of sewage and other fluids in the interior of the tank. At least one annular projection (52) extends around an outlet opening (44) to enable a tank wall portion (54) adjacent the outlet opening and outlet tubing (48) to move relative to the remainder of the tank.

Abstract: A corrugated, thin walled plastic tank is ideally suited for subterranean storage and transmission of sewage and other materials. The tank has a bottom wall which terminates in a peripheral edge disposed in a horizontal plane. A corrugated, peripheral wall extends upward from the peripheral edge to an apex area. The corrguations of the peripheral wall include alternating crown and root portions. A peripheral rib extending circumferentially around the peripheral wall is defined by a plurality of rib portions which are disposed in the root portions of the corrugations. Each rib portion has a rib outer portion which is substantially flush with the adjoining crown portions and rib side portions which extend from the rib outer portion into the adjacent root portion. An indentation area is formed by enlarging one of the root portions. An annular sleeve depends from the indentation area into the interior of the tank to provide a fluid access with the interior of the tank.

Abstract: A thin-walled, one-piece plastic tank for subterranean storage and transmission of sewage or other materials. The tank comprises a bottom wall, an arched top wall and opposed end walls. The top wall is substantially semi-circular in cross-section with a plurality of corrugations therearound. Along the apex area of the arch is a pair of manhole-like openings with an arced strengthening rib therebetween. The bottom wall is generally arced in cross-section with a radius very large compared to the radius of the cross-section of the top wall which causes the bottom wall to be generally flat. The end walls are arced in the longitudinal, cross-sectional and horizontal planes. The end walls each have a plurality of corrugations. In the root of one of the corrugations is a depression which contains a horizontal aperture for the egress or ingress of fluid materials. The bottom wall has a plurality of corrugations mating with the top wall corrugations such that the corrugations circumscribe the tank.