Patent ID: 7128088

Claim:
A backflow preventer, said backflow preventer comprising: a housing having a passage therethough and a valve seat; at least one valve positioned in the passage, said at least one valve resiliently biased for closure with the valve seat to prevent fluid flow in a direction and to allow fluid flow in a reverse direction, said at least one valve includes a stem extending from a valve head engaging the valve seat, the stem having an outer surface with a hump extending radially outward from the outer surface along a portion of the outer surface; and a valve guide, said valve guide guides the stem during opening and closing of said at least one valve, said valve guide including a bushing having at least one retention member, said at least one retention member engaging the outer surface of the stem, wherein said hump on the outer surface of the stem causes a higher friction loss during engagement with the at least one retention member than other portions of the outer surface of the stem during opening and closing of said at least one valve.