U.S. Seal Shaft Seal Assembly (Generic), PS-3890

The U.S. Seal PS-3890 is a generic shaft seal assembly for Hayward Northstar pumps manufactured between 1998 and 2007. It is written both as PS-3890 and as PS3890 in parts listings, and it is offered as an alternative to the Hayward factory seal.

What the shaft seal does

It seals the pump shaft where it passes from the wet end into the motor. The assembly has two faces, one that turns with the shaft and one that stays with the housing, running against each other to hold water back.

When to replace it

A drip or a puddle between the pump body and the motor is the tell. So is a pump that has been run dry, since the seal faces rely on water for lubrication and a dry run can ruin them in seconds. Change it promptly: water tracking into the motor end takes the bearings with it.

Fitting

Both halves are supplied together and should always be fitted as a pair, never mixed with the old faces. Keep the sealing surfaces clean and free of grease as you assemble.