Sta-Rite O-Ring, Adapter Bushing, 35505-1423

The Sta-Rite 35505-1423 is the o-ring for the air relief adapter bushing on System 3 filters. It is the genuine Sta-Rite part, and it is common across the System 3 range: the S7S50 and S8S70 sand filters, the S7M120, S7M400, S8M150 and S8M500 cartridge filters, the S7D75 and S8D110 DE filters, and the SMD series modular DE filters.

Why this one leaks first

The air relief sits at the highest point of the tank, which is where trapped air collects and where the assembly is opened most often. Every time the bushing is worked, the o-ring is compressed and released, and chlorinated water and sun harden it from the outside in. Once it takes a permanent set it no longer fills the groove and water begins to seep out of the top of the filter.

Fitting

Clean the groove, seat the new o-ring fully so no part of it stands proud, and tighten the bushing evenly. An o-ring caught on the edge of the groove will be pinched and will leak straight away.