Hayward OEM O-Ring for Filter Head, CX800F

The Hayward CX800F is the filter head o-ring for the Star-Clear II cartridge filter, in the C800, C1100 and C1500 sizes. It measures 9-1/2 inches in diameter and is a genuine Hayward part.

Where it sits

This is the large seal on the joint between the filter head and the filter body. It has to hold that whole seam against system pressure, which is why a tired one shows up as a steady weep or spray right at the split line.

Replace it with the cartridge

The seal is disturbed every time the filter comes apart. It stretches, takes a set in the groove, and eventually stops sealing on reassembly. Since the housing is already open when you service the cartridge, that is the moment to put a fresh o-ring in rather than reuse the old one and open it all up again.

Fitting

Clean the groove and the mating face before the new seal goes in, and use a lubricant intended for pool o-rings. Petroleum products attack the rubber and shorten its life.