850 Gallon Underground Cistern Water Storage TanksCistern tanks are intended for bulk storage or collection of potable water and designed for below ground level installations. Tanks are manufactured from high-density polyethylene with U.V. inhibitors and feature a trapezoidal, deep rib design. Tanks feature a custom-molded gasket in the lid. Manufactured from extruded Nitrile rubber, the gasket snaps into the lid and ensures a watertight seal. Our exclusive lid design locks in place with nylon ties, eliminating the need for metal fasteners that can corrode and fail. Cistern tanks are FDA-approved for potable water and are manufactured for containment of liquids up to 1.7 specific gravity.