Patent ID: 7144506

Claim:
A blow-molded septic tank having an interior, an exterior, an upper surface, a lower surface, and two ends, said tank comprising: a plurality of integral, circumferential ribs formed in the tank's upper surface and lower surface, each rib depressed into the interior of the tank, wherein each of said ribs incompletely encircles the tank to form an upper gap and a lower gap in each rib; wherein the upper gap of each rib is circumferentially offset relative to the upper gap of each adjacent rib, such that said upper gaps form a serpentine gas pass-through channel in the upper surface of the tank; wherein the lower gap of each rib is circumferentially offset relative to the lower gap of each adjacent rib, such that said lower gaps form a serpentine liquid pass-through channel in the lower surface of the tank; flange portions on the exterior surface, formed in the depression of each rib; and at least one service opening to the interior of the tank.