Pentair O-Ring, Drain Plug

This is the genuine Pentair drain plug o-ring for the Letro booster pump, the new style seal. Pentair carries it under two numbers, LA375 and O-446, and both point at this part.

What it seals

The drain plug at the bottom of the booster pump volute. That plug comes out at every winterization and goes back in every spring, and its rubber o-ring is what stops water passing the threads.

The symptom

A slow drip or a wet patch under the pump that will not stop no matter how hard the plug is tightened. Once the o-ring has hardened and taken a permanent set, extra torque only cracks the plug or the housing. A fresh seal is the fix.

Fitting

Wipe the seat clean, put a thin film of silicone lubricant on the new o-ring, and hand tighten the plug. It does not need to be forced.