3" Swing Check Valve allows water to flow in only one direction in a hose or pipe. These install near your skimmer or filter, so if the pump is turned off, it will not back-siphon and dry up. Also used to help with priming an external pump. Used on the intake to keep water in the pipe. The 'swing style' Triton Check Valve features a 2" socket union on the inlet, 2" or 11/2" socket unions for the outlet, a molded in 90_ elbow, and a slim design that allows clearance when installed with direct drive pumps.