Sta-Rite O-Ring, 2-3/8″ ID, Adapter to Tank, PLM/PLD, 35505-1424

This is the Sta-Rite 35505-1424 adapter to tank O-ring, the seal between the filter adapter and the tank on PLM and PLD style filters. It measures 2-3/8 inches inside diameter with a 3/16 inch cross section.

Why it fails

An O-ring in this position spends its life compressed, warm and in chlorinated water. Over a few seasons it takes a permanent set, hardens and loses the springiness that made it seal. The result is a slow weep at the adapter that shows up as a wet spot on the pad or a drop in pressure as the filter pulls air.

Model coverage

It is listed across a broad run of Sta-Rite filters: the System 3 sand models S7S50 and S8S70, the System 3 cartridge models S7M120, S8M150, S7M400 and S8M500, the System 3 DE models S7D75 and S8D110, and the System 2 modular media PLM100 and PLM150. It is also listed for AquaTools permanent media AT84100 and AT84150 and the AT8230 and AT8236 DE filters.

Fitting

Clean the groove and the mating face before the new ring goes in, and use a silicone lubricant made for pool equipment. Petroleum based grease attacks the material and will have you back at the same joint next season.