Tank precharge pressure check valve

Claim 1

A tank precharge check valve comprising a fixture attached to and having direct access to a tank normally maintained at a predetermined pressure by means of a pump, a column on said fixture open with respect thereto so that liquid is located in the column, a check valve member floating in said column on said liquid, a check valve seat in said fixture opposite the connection thereof to the tank, and a venturi tube extending from the tank to the upper portion of said vertical column, whereby under normal conditions the check valve member normally floats in the column, but upon substantial depletion of liquid in the tank, air will pass through the venturi tube into the column, forcing the check valve member down against said check valve seat, closing the demand line and the air against escaping, wherein said venturi tube is constructed and arranged to provide for sucking air from the top of the vertical column when liquid is supplied to the tank, allowing the check valve member and the liquid to rise into the column upon restoration of normal operation.