Series Governor 80 Ball Cock and Thermal Expansion Relief Valves are triple-function devices: a toilet tank ball cock, an anti-siphon backflow preventer and a thermal expansion pressure relief valve. The Governor 80 limits the domestic water system's preset static pressure, protects the temperature and pressure relief valve on the water heater, reduces the requirement for a thermal expansion tank or an auxiliary relief valve and prevents backflow from water closets. Relief Valve Set At: 80psi.