Pentair Piston Assembly O-Ring, 35505-1318

The Pentair 35505-1318 is the piston assembly O-ring for the Sta-Rite WC212-134 push pull valve. It has a 2-1/2 inch inside diameter and may also fit other Sta-Rite valves.

What it fixes

A push pull valve seals by sliding a piston through a bore, and it is the O-rings on that piston that make the seal. When one hardens, flattens or picks up a nick, water bypasses the piston, and the symptom is a valve that no longer isolates properly in one or both positions.

Fitting it

Measure the inside diameter of the old ring against the 2-1/2 inch figure to confirm the match. A silicone based O-ring lubricant on assembly helps the ring seat cleanly and stops it tearing as the piston goes home.