What are the most common pool pump problems?
The most common pool pump problems are loss of prime (air getting in so the pump cannot pull water), a humming motor that will not start (usually a dead capacitor), water leaking from the pump, and a motor that is loud or completely dead. Each has a clear set of suspects, so the trick is to match the symptom to the cause before you spend money.
Before you touch anything electrical, turn the pump off at the breaker, not just the timer. Pool pumps run on 115V or 230V and the motor can hold a charge in the capacitor even after the power is off. If you are not comfortable working near line voltage, the motor and electrical repairs below are the point to call a pro. The plumbing-side fixes are safe for any pool owner.
Why is my pool pump not pulling water or losing prime?
A pump that loses prime is almost always sucking air somewhere on the suction side, between the skimmer and the pump. The pump can only move water if its basket housing stays full, so any air leak lets the water drain back and the impeller spins on air. The tell is a pump basket that runs half empty with bubbles, or water that returns weakly to the pool.
Check the easy things first. Make sure the water level is above the middle of the skimmer, because a low level lets the skimmer gulp air. Empty the pump basket and the skimmer basket; a clogged basket starves the pump. Then look hard at the pump lid o-ring: if it is dry, cracked, or out of its groove, it pulls air. Clean it, coat it with a silicone pool lube, and make sure the lid seats flat. A loose lid is the single most common cause of a pump that will not hold prime.
If it still sucks air, the leak is upstream. Inspect the suction-side unions, the valves, and the threaded fitting at the pump inlet for cracks or dried-out Teflon tape. A pump that lost prime after sitting dry can also need to be filled: open the lid, fill the basket housing with a hose, reseal, and let it catch. Persistent air can also mean a clog farther back, which often shows up as the cloudy water covered in our cloudy pool guide when circulation drops.
Why is my pool pump humming but not starting?
A pump that hums but will not spin almost always has a failed start capacitor. The capacitor is the small cylinder under the cover on top or back of the motor, and it gives the motor the jolt it needs to start turning. When it dies, the motor gets power and hums but cannot start the rotation, and it will overheat and trip if you leave it like that.
You can confirm it with a simple test: with the power off, try to spin the motor shaft by hand using the slot on the back end. If the shaft turns freely but the motor only hums under power, the capacitor is the likely culprit. A replacement capacitor runs about $15 to $30 and swaps in with a screwdriver and a nut driver, but it stores a charge, so discharge it across an insulated screwdriver before touching the terminals. Match the microfarad (uF) and voltage rating printed on the old one exactly.
If the shaft will not turn by hand, the problem is deeper: seized bearings, a jammed impeller, or a burned winding. A small piece of debris can lock the impeller, which you reach by opening the pump and the seal plate. If the impeller is clear and the shaft is still locked, you are looking at a motor replacement rather than a quick part swap.
Why is my pool pump leaking water?
Where the pump leaks tells you which seal failed. Water dripping from under the motor, between the wet end and the motor, is a worn shaft seal, the most common leak. The shaft seal is a two-part mechanical seal that keeps water out of the motor, and it wears out over years or gets wrecked if the pump ever ran dry. Left alone, that water gets into the motor bearings and destroys the motor, so a leaking shaft seal is worth fixing promptly.
Leaks at the pump lid or at the unions are simpler: a dried-out o-ring or gasket. Replace the lid o-ring, the diffuser o-ring, or the union o-rings, lube them with silicone, and snug the connections by hand. Do not over-tighten plastic unions, because cracking the housing turns a cheap fix into a new pump. A shaft seal kit is usually $10 to $20, but replacing it means pulling the motor and seal plate, so it is a step up in difficulty from o-rings.
How can I tell if the pool pump motor is burned out?
A burned-out pool pump motor usually announces itself: it trips the breaker the moment it starts, gives off a burnt or fishy smell, sounds like grinding or screeching, or does nothing at all with power confirmed at the terminals. A motor that runs hot enough to shut off after a few minutes and then restarts once cool is overheating, often from failing bearings or a wiring fault.
Loud grinding or a high-pitched squeal is failing motor bearings, which you can sometimes replace but often signals the motor is near the end. First rule out the simple stuff: many pumps and their GFCI outlets have a reset, so check for a reset button on the motor or pop the breaker and GFCI before assuming the worst. If power reaches the motor, the capacitor is good, the shaft is free, and it still will not run, the windings are likely burned out and the motor needs to be replaced.
When you replace a motor or the whole pump, size it to your pool rather than just matching the old horsepower, since most pools are over-pumped. Our best pool pump guide covers variable-speed options and sizing, and keeping the pump on the routine in the pool maintenance schedule is what makes the next one last.
Is it worth repairing a pool pump or replacing it?
Repair the pump when the fix is a capacitor, a shaft seal, an o-ring, or a basket, because those parts cost $10 to $40 and restore a sound motor. Replace it when the motor is burned out, the bearings are gone, or the housing is cracked, especially if the pump is single-speed and more than 8 to 10 years old.
The math usually favors replacement on an old single-speed pump. A new motor is often $150 to $300 installed, while a full variable-speed pump runs more up front but cuts running costs by a large margin and may qualify for a utility rebate. If you are paying for labor either way, putting that money toward a modern variable-speed pump tends to pay back faster than nursing an old energy-hog motor along.
Frequently asked questions
Do pool pumps have a reset button?
Many do. Pool pump motors often have a thermal overload that resets itself after the motor cools, and some have a manual red reset button on the motor housing. The pump's power is also usually on a GFCI breaker or outlet that can trip, so before assuming the motor is dead, check the breaker, the GFCI, and any reset button on the motor.
How much does it cost to repair a pool pump?
Small DIY repairs are cheap: a capacitor is about $15 to $30, a shaft seal kit $10 to $20, and o-rings a few dollars. A replacement motor is roughly $150 to $300 installed, and a full variable-speed pump costs more up front but cuts running costs. The repair is worth it when a cheap part fixes a sound motor; replacement makes sense once the motor or housing is gone.
How can I tell if my pool pump is burned out?
A burned-out pump trips the breaker on startup, smells burnt, grinds or squeals, or does nothing with power confirmed at the terminals. First rule out a tripped breaker or GFCI, a dead capacitor (the motor hums but will not start), and a jammed impeller. If power reaches the motor, the capacitor is good, and the shaft turns freely but it still will not run, the windings are likely burned out.
Why is there no water flowing through my pool pump?
No flow almost always means the pump lost prime by sucking air on the suction side. Check that the water level is above the middle of the skimmer, empty the pump and skimmer baskets, and inspect the pump lid o-ring, which is the most common air leak. Refill the basket housing with a hose, reseal the lid, and let the pump catch prime.
How do I shock a pool if the pump is not working?
You can still shock with the pump down, it just works slower. Pre-dissolve granular shock in a bucket of water, pour it around the pool, and brush vigorously to move the water and spread the chlorine, since there is no circulation. Get the pump running as soon as you can, because chlorine needs the filter to clear the water. Use the chlorine calculator to set the amount for your volume.