Description

The SuperPro O-39-9 is a universal o-ring with a 1/2 inch inside diameter and a 3/32 inch cross section. It is not tied to one piece of equipment, it is a stock size that shows up on drain plugs and small fittings across pumps, filters and booster pumps.

Buying by measurement, not by model

Because this is a generic size, the right way to order it is to measure. Take the inside diameter of the old ring across the hole, then the thickness of the rubber. If those come to 1/2 inch and 3/32 inch, this is the ring. The same part is cataloged as P40, O-39-9 and U9-359, and a long list of substitute numbers from other suppliers points at the same size.

Fitting it

Clean the groove before the new ring goes in, and dress it with a silicone based o-ring lubricant. Petroleum grease is the common mistake here, it swells the rubber and shortens the life of the ring. A drain plug that has started weeping is usually the ring rather than the plug, so this is worth trying before replacing anything larger.