Valterra 200-C15 1-1/2 in Clear Slip x Slip Swing-Spring Check ValveStop backflow in 1 1 2" PVC pool and spa plumbing with the Valterra 200 C15 swing spring combo check valve (slip x slip). It pairs a flapper with a light 1 2 lb spring to keep one way flow steady at low rates without adding much resistance. The clear PVC body lets you verify operation at a glance, and the solvent weld sockets make swaps into existing lines straightforward.