A leaking pool pump shaft seal is the most common — and most preventable — cause of a $400+ motor replacement. Water dripping from the seal between the wet end and the motor gets into the motor bearings, rusts the shaft, shorts the windings, and ends the motor’s life. Catch it early and you spend $30–$50 on a seal kit and an hour of your Saturday. Catch it late and you’re shopping for a new motor.
When the shaft seal is failing
- Visible water drip from the underside of the pump, between the wet end and the motor.
- White or green corrosion on the motor face plate.
- Motor running louder than usual (water has reached the bearings).
- Rusty smell from the motor when it runs.
- Visible water mist around the pump during operation.
What you’ll need
- A new shaft seal kit matched to your pump model
- A new pump body o-ring or gasket (always replace these together)
- Silicone-based pool lubricant
- A 9/16″ or 1/2″ socket wrench (depends on pump model)
- Channel-lock pliers and a flat screwdriver
- A clean rag
- Optional but recommended: a strap wrench or oil-filter wrench for stuck impellers
Step-by-step: replacing the shaft seal
Turn the pump off at the breaker. Close the suction-side valves and the return valve so water doesn’t pour out when you separate the housing.
Open the pump’s drain plugs (usually two, at the bottom of the housing). Let it drain fully. Loosen the pump lid to break vacuum.
The pump has a series of bolts (typically 4–8) holding the motor seal plate to the strainer pot. Loosen them in a star pattern and pull the motor + seal plate assembly straight back. You’ll see the impeller exposed once it’s clear.
The impeller threads onto the motor shaft in the “reverse” direction — meaning it spins counter-clockwise to remove. Hold the motor shaft from the back (most motors have a flat or hex on the back end) and rotate the impeller counter-clockwise. If it’s stuck, use a strap wrench around the impeller; never pliers, which damage the vanes.
The shaft seal is in two halves: a rotating half embedded in the impeller hub, and a stationary half pressed into the seal plate. Pry the seal plate’s half out gently with a flat screwdriver. Pop the impeller’s half off the impeller hub (it usually lifts straight off). Clean both seats with a rag.
The new seal kit has two pieces — one for each side. Apply a thin film of silicone pool lubricant to the rubber boot of each half. Press the stationary half into the seal plate by hand, making sure the polished ceramic face is OUT (the side that meets the carbon face on the rotating half). Press the rotating half onto the impeller hub the same way.
Thread the impeller back onto the motor shaft (clockwise to tighten). Hand-tight is enough; the pump’s rotational direction self-tightens during operation.
The o-ring or gasket between the seal plate and the strainer pot is reused at your peril. Drop in a new one, lubricated with silicone.
Slide the motor + seal plate assembly back into the strainer pot. Reinstall the bolts in a star pattern, snug them in two passes (first finger-tight, then to spec). Reinstall the drain plugs.
Open suction and return valves. Re-prime per our priming tutorial. Run the pump for 5 minutes and inspect for drips at the seal area. Dry = success.
Pump-specific seal kits in stock
Pentair Sta-Rite DuraGlas Seal Kit (PP1016)
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Pentair 7/10HN Shaft Seal Kit (PP1551)
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Magic Lube II Silicone 1 oz
Shop NowHow long does the new seal last?
A properly installed shaft seal lasts 3–7 years in a residential pool, depending on water chemistry and how many hours per year the pump runs. The biggest enemies are pH below 7.0 (acidic water erodes the ceramic face) and running the pump dry (the seal needs water for cooling and lubrication). Get both right and you may never replace this seal again.
Not sure which seal kit matches your pump? Send PST Pool Supplies the pump model number from the motor data plate and a photo of the pump body, and we’ll match the right seal kit on the first try.