Abstract:
A vacuum breaker is provided comprising a body member having an inlet and an outlet defined therein. A core insert member may be threadedly engaged within the body member having a chamber defined therein. A vent passage is defined within the body member to vent the outlet side of the device to atmosphere. A piston member is movably disposed within the chamber between an upper limit stop and a lower limit stop so as to variably restrict liquid passage through the device. At its lower limit stop, the piston essentially seals the inlet from the outlet while the vent passage vents the outlet to atmosphere. At its upper limit stop, the piston essentially seals the vent passage from the outlet. A drain passage is defined within the device generally between near the top portion of the chamber and the outlet so that liquid entrapped within the chamber above the piston member drains through this drain passage to the outlet side of the device during movement of the piston within the chamber. In this manner, liquid entrapped above the piston member is prevented from being pumped out of the device during movement of the piston.