Swimables Replacement for Pentair Backwash Valve Piston Assembly | 51013811 | SW-26-130The Swimables Replacement for Pentair Backwash Valve Piston Assembly (Part #SW 26 130) with O Ring, is a compatible replacement for Pentair 51013811, designed for select Pentair push pull slide backwash valves. This complete piston assembly restores proper valve operation by controlling internal water routing during filter and backwash cycles. It is commonly used in compatible Pentair 2 inch push pull slide valve assemblies, including valve model