DEWALT Full-Flow Sump Pump Check Valve. Features easily slip-fit, boot-grip connections for 1-1/4-inch or 1-1/2-inch sump pump discharge pipes. It is built tough for longevity using trusted ABS plastic, flexible rubber, and corrosion-resistant stainless steel clamps. The full-flow design with a heavy-duty weighted flapper maintains the sump pump's performance and prevents backflow, which can cause short cycling. Backed by a leading 1-year limited warranty.