Abstract: A valve assembly including a first housing member having a flange and a second housing member having a flange. The first housing member is connected to the vacuum milking system. A flexible diaphragm is mounted between the flanges of said first and second housing members. The diaphragm is movable between an unflexed position and a flexed position in response to forces exerted on opposite sides thereof. A control valve is operable to selectively place the second housing member in communication with the atmosphere wherein the diaphragm is forced to assume its unflexed position and to periodically place the second housing member in communication with the vacuum in the vacuum line to thereby force the diaphragm to assume its flexed position. A valve member is mounted on the diaphragm and is operable to place the first housing in communication with the atmosphere when the diaphragm is in its flexed position to thereby admit air into the vacuum line.