Sta-Rite O-Ring 2-1/8″ ID, 35505-1428

Sta-Rite 35505-1428 is a replacement o-ring measuring 2-1/8 inches inside diameter with a 1/8 inch cross section. It is listed under Sta-Rite System 3 cartridge filter parts, covering models S7M120, S7M400, S8M150 and S8M500, and is identified in the listing as the large elbow o-ring.

Size is the whole story

An o-ring that is close but not correct will seem to seal on assembly and weep under pressure. Check both numbers against the ring you are replacing: 2-1/8 inches across the inside, 1/8 inch thick.

While the filter is open

Seals harden, flatten and take a permanent set from years of compression. They are the cheapest part in a filter and the most common source of a drip. Any time the filter is apart for a cartridge clean, the o-rings are worth a look.