Canplas 223285W PVC Backwater Valve with 16-Inch Access Sleeve and ABS Lid, 4-Inch Protection against the backflow of sewage and storm water Compact, lightweight and easy to install All Canplas Backwater valves are socket x socket with all sockets being DWV Acme threads provide positive traction and extra strength Neoprene O-ring effectively seals valve lid