Sta-Rite Position Lock Ring, Modular Filter, 27001-0054S

The Sta-Rite 27001-0054S is the position lock ring, also called the Posi-Lok ring, for System 2 modular media filters. It is the genuine Sta-Rite part.

What it does

The filter tank is built as an upper and a lower half. The lock ring goes around the joint between them and holds the two together against the pressure inside. Everything the filter does depends on that ring staying intact.

Dimensions

The inside diameter is approximately 16 in. The inner lip, the part that grips the tank flange, is approximately 3/4 in. thick. Sta-Rite used more than one ring size across the modular filter range, so compare those measurements with your old ring before ordering.

When to replace it

Sun and years of clamping load make the plastic brittle. A ring that has cracked, split or lost its shape has to be replaced rather than coaxed back on, since it is the only thing keeping a pressurized tank closed.