CMP 2″ Pump Union Ribbed T-Gasket, 21023-030-000

The CMP 21023-030-000 is the ribbed T-gasket for 2 inch pump unions, made by Custom Molded Products.

How it seals

A union joins two pipe halves with a threaded collar. The gasket does the actual sealing, not the collar. This one has a T shaped section: the stem locates in the groove so the gasket cannot creep out of position, and the flange is squeezed between the two faces as the collar is tightened.

When to replace it

Union gaskets harden, flatten and take a set. The symptom is a union that keeps weeping no matter how hard the collar is turned, and the common mistake is to keep turning. That splits collars and does nothing for the leak. Fit a new gasket, tighten by hand until it just stops, and the joint seals. Because unions get opened every time a pump comes off the pad, it is worth keeping a spare.