Why is my pool pump humming but not running?

A pool pump that hums and does not turn is most often jammed or starved of power, not dead. The usual suspect is debris wedged against the impeller. Other causes are a worn motor or low voltage at the motor. Switch the pump off at its breaker or switch rather than letting it hum, then have a pool pro open it up.

Why a humming pump is worth switching off

The hum is the motor trying to turn a shaft that will not move. Current flows, nothing spins, and the windings heat up. Hayward's Super Pump motor has an automatic thermal overload protector: the motor shuts off if the power supply drops, before heat damage can burn out the windings, and it restarts on its own once it has cooled.^[1] The manual adds that it will keep cutting on and off until the problem is corrected, so be sure to correct the cause of the overheating.^[1]

That cycle is the sign of a pump you should stop running. Each attempt adds heat to a motor that may be perfectly good.

The likely causes, most common first

A jammed impeller. Hayward's troubleshooting guide lists an impeller jammed with debris as the first thing to check when the motor hums but does not start.^[1] Leaves, pool toys, small stones and bits of broken basket can get past the strainer and lock the impeller. The manual's fix is to have a qualified repair professional open the pump and remove the debris.^[1]

Low voltage or a weak supply. The same guide traces a motor that shuts off to low voltage at the motor or a power drop, frequently caused by undersized wiring or extension cord use, and says to contact a qualified professional to check that the wiring gauge is heavy enough.^[1] Hayward warns the voltage at the motor must not be more than 10% above or below the nameplate rating, or the motor may overheat, causing overload tripping and reduced component life.^[1]

An old or worn motor. ENERGY STAR lists a pump that "hums or buzzes but will not start" among the warning signs that it may be time to call a pool services contractor, alongside a pump that is seven to ten years old, does not seem as powerful, makes continuous noise, gets hot and shuts off, or starts slowly.^[2] On an older pump, a hum on top of those symptoms points toward the motor, and the repair-or-replace question in is it worth fixing a pool pump motor becomes the real one.

A leaking shaft seal. Hayward warns that running a pump without water may damage seals, causing leakage, flooding and a voided warranty.^[1] Its manual also says chlorinated water that gets past a damaged seal can wipe out the grease in the motor bearings and make them whine.^[1] A pump that was run dry, or one with a drip at the seal, can end up with a seized or noisy motor.

What not to do

Do not keep switching the pump back on to see if it catches. Do not pry at the pump with the power on, and do not run it from an extension cord. Hayward's manual says hazardous voltage can shock, burn, and cause death or serious property damage, and to turn off the power supply before working on any electrical equipment.^[1] It also says its pump should be installed and serviced only by a qualified professional.^[1]

A pool pump circuit sits next to water, so the stakes are higher than a typical appliance. Pump work is a plumbing job at the wet end and an electrical job at the motor, and a pro will tell you which half you have.

What to tell the pro

A short description saves a visit. Say when it started (after a storm, after a vacuum clean, after a cold snap, after a power cut), whether the pump hums at once or after a delay, whether the breaker or GFCI has tripped, whether the strainer basket is cracked, and how old the pump is. Say if you have noticed water dripping under the motor. Ask the business to find the cause before quoting a motor, because a jammed impeller is a much smaller job. How much pool pump repair costs in Virginia covers what drives the price, and what replacing a pool pump motor involves covers the bigger job.

When to call a licensed pro

Call as soon as the pump hums without turning, since the cause is inside the pump or the motor wiring. In Virginia no individual may work, or offer to work, as an electrical tradesman without a tradesman licence, unless working under the supervision of a tradesman licensed in that specialty.^[3][4] DPOR also says that if the work is valued at $1,000 or more, a valid Virginia contractor's licence is required for the licence category in which the contractor is to work.^[5] Look up the business and, for wiring, the electrician in DPOR's licence search; how to check if a contractor is licensed in Virginia shows how.

DPOR advises getting at least three written bids or estimates using identical plans and specifications so you can compare prices and contractors.^[5] For a pump, that means the same diagnosis, the same parts and the same warranty terms.

Loclis lists DPOR-licensed businesses with their licence number and class. Browse pool and spa equipment answers or find pool and spa businesses near you.

To have licensed local businesses quote the job, describe the pool pump problem once.