Description

The Hayward CX900W is the knob washer used on Star-Clear Plus cartridge filters and Pro-Grid DE separation tanks. It is the genuine Hayward part.

Where it goes

The washer sits under the clamp knob and spreads the load where the knob bears down. It is a small piece, but without it the knob presses directly on the clamp, which means the clamp never draws evenly and the filter head does not seal the way it should.

Order two

Hayward specifies a quantity of two, so a filter needs a pair. If you are chasing a leak at the clamp, look at the filter head lid o-ring and the knob o-ring while you are in there, because a clamp area leak is usually one of those three parts.