Storage Tank Overflow Valve

Overflow Valves are installed in the overflow outlet pipe of an underground water storage tank to prevent insects, rodents, flood water, and other contaminants from entering the tank.

Unlike U-traps which rely on a water seal, they completely block the outlet pipe, provide easy access for maintenance, and are unaffected by long periods of dry weather than can cause water seals to evaporate.

In dry weather, a heavy flapper disc supported by an EPDM rubber hinge rests over the valve inlet port. When the tank overflows during a rain storm, the flapper disc swings upward and allows the water to flow freely through the valve to the outlet port. The entire flapper assembly can be removed for cleaning or replacement by unscrewing a gasketed cleanout cap and lifting the handle. All parts are made of thick industrial gray PVC. Standard sizes have socket fittings to fit 4” or 6” PVC pipe; standard risers are 24”or 48” with inverts listed below: