Your pool pump hums but will not start, runs with air in the basket, or will not catch prime, and the water has stopped moving. Most pool pump problems come down to power, an air leak on the suction side, or a clog, and you can check all three without special tools. This page explains how the pump works, which parts fail, the numbers from the Hayward, Pentair and Jandy manuals, and where DIY should stop.
How does a pool pump work?
A pool pump is a motor that spins an impeller (a small plastic fan wheel) inside a sealed housing. It pulls water from the skimmers and main drain, pushes it through the filter and heater, and sends it back through the return jets.
- Water comes in on the suction side. Skimmers and the main drain feed the pump. Any air leak on this side gets pulled straight in.
- The strainer basket catches debris. Leaves and hair stop in the basket under the clear lid.
- The impeller pushes water out. It throws water out under pressure toward the filter.
- The shaft seal keeps water out of the motor. Water cools and lubricates the seal, so running the pump dry ruins it.
- Priming fills the system with water. A self-priming pump can lift water from below, but only when the strainer pot starts full. Hayward says any self-priming pump will not prime if there are suction air leaks.
- Thermal overload protects the motor. On Hayward motors, it shuts the motor off when it overheats and lets it restart once it cools, over and over until you fix the cause.
Which pool pump parts fail, and what are the signs?
| Part | What it does | Sign it is failing |
|---|---|---|
| Lid O-ring | Seals the strainer lid against air | Air in the basket, bubbles at the return jets, pump loses prime |
| Strainer and skimmer baskets | Catch leaves before the impeller | Low flow, a half-empty strainer pot, a rough-sounding pump |
| Impeller | Moves the water | Weak flow, or a motor that hums and will not turn when debris jams it |
| Shaft seal | Keeps water out of the motor | Drip or puddle under the pump between the motor and the wet end |
| Motor bearings | Let the shaft spin smoothly | Screeching or grinding that gets louder over weeks |
| Start capacitor (many single-speed motors) | Gives the motor a kick at startup | Motor hums but the shaft does not spin; the breaker may trip |
| Suction valves and unions | Join pipes and control flow | Slow priming, bubbles at the returns, a hiss near a fitting |
What should I check first when my pool pump is not working?
- Power. Check the breaker, the GFCI (ground-fault circuit interrupter, which cuts power when current leaks) and any timer. Hayward lists these first when a motor will not start.
- Water level. Pentair warns that if the water falls below the suction port, the pump draws air, loses prime and runs dry.
- Baskets. Empty the skimmer and pump baskets. Pentair says to look at the strainer basket at least once a week.
- Lid and O-ring. Clean the O-ring, check it for cracks, lube it with the lubricant your manual names, and seat it in its groove. This is Hayward’s first fix for a pump that will not prime.
- Valves. Hayward says all suction and return valves must be open while the pump runs.
- Filter pressure. A high gauge reading with weak flow means the filter needs cleaning, not the pump. See pool filter problems.
- Shaft spin. With the breaker off, see whether the motor shaft turns by hand. If it will not, the impeller is jammed or the bearings have seized.
Safety first. Turn the pump off at the breaker before you open the lid or touch wiring. Pentair warns never to open the strainer pot on a pump that failed to prime or ran dry, because it can hold pressure and scalding water; open the valves and wait until the pot is cool. If the GFCI trips again after a reset, leave it off and call an electrician. Never blow out lines with high-pressure air (Hayward says below 5 PSI only). If a drain or suction cover is missing or cracked, keep everyone out of the pool, because suction outlets can trap hair, limbs and jewelry.
Pool pump numbers to know
These numbers come from the makers’ manuals for the Hayward Super Pump 700 Series, the Pentair SuperFlo and the Jandy VS FloPro. Other models differ, so check your pump’s label and manual.
| Spec | Hayward Super Pump | Pentair SuperFlo | Jandy VS FloPro |
|---|---|---|---|
| Electrical protection | Only on a GFCI-protected branch circuit | Only on a GFCI-protected branch circuit | See your model’s manual |
| Height above water | Self-priming to 10 ft (two-speed motors on high only) | Install no more than 10 ft above the water | Certified to prime up to 10 ft above the water at sea level |
| Priming time | Up to 10 minutes; if not primed in 5, stop and find the cause | Fill the pot before starting; see your model’s manual for time | About 14 to 15 minutes at the default 2,750 RPM priming speed at 10 ft above the water; within 6 minutes at 3,450 RPM |
| Distance from pool | Power disconnect at least 5 ft from the pool’s inside wall | Pump at least 5 ft from the pool’s inside wall | See your model’s manual |
| Strainer basket | Clean regularly; do not strike it | Look at it at least once a week | See your model’s manual |
| Lid O-ring | Clean and lube with Jack’s 327 each time the lid comes off | Keep clean and well lubricated | See your model’s manual |
| Voltage at the pump | Within 10% of the nameplate rating | See your model’s manual | See your model’s manual |
Hayward vs Pentair vs Jandy: what changes when you troubleshoot?
All three brands use the same layout: strainer pot, impeller, shaft seal and motor, so the checks above work on any of them. Jandy is part of Fluidra, the same group as Zodiac and Polaris.
The lid is the first difference. The Hayward Super Pump lid tightens with hand knobs (no wrenches), while the Pentair SuperFlo uses a clamp you turn clockwise until the handles sit level. Variable-speed pumps add a control panel and a set priming speed; on the Jandy VS FloPro, raising that speed cuts priming time a lot when the pump sits well above the water. Parts are the second difference: impellers, seals, O-rings and baskets rarely swap between brands, or even between models. Write down the model number from the pump label and motor nameplate before you order.
When should you call a pool or spa pro?
- A jammed impeller. If the motor hums and the shaft will not turn, Hayward says to have a qualified repair professional open the pump.
- A leaking shaft seal. Hayward says to replace leaking seals at once, before water reaches the bearings.
- GFCI trips, burning smells or low voltage. These need an electrician and a meter.
- A clogged suction line. A pro can read the vacuum at the strainer cover with a gauge; Hayward expects 5 to 6 inches.
Pool pros bill by the visit or by the hour, so doing the free checks first keeps the bill smaller.
Common questions
How do I reset a pool pump motor?
Most single-speed pool pump motors have no reset button. Reset the breaker or GFCI and check the timer. Hayward motors restart by themselves once the thermal overload cools, so a pump that keeps shutting off is overheating and needs the cause found. Variable-speed pumps have their own alarms; follow your manual.
How do you know if your pool pump is blown?
A pump is likely done if power reaches the motor, the shaft will not turn by hand, and it hums or trips the breaker. Loud grinding bearings also point to the motor. Rule out a jammed impeller first, since it looks the same from outside.
What do you do if your pool pump won’t prime?
Turn the pump off, fill the strainer pot with water, clean and lube the lid O-ring, and close the lid tight. Open the valves and the filter’s air relief valve, then start the pump. Hayward says priming can take up to 10 minutes, but if it has not primed in 5, stop and look for an air leak, a clog or low water.
Why won’t my pool pump stay primed?
A pump that primes and then loses it is almost always pulling air. Check the lid O-ring, then the unions and valves on the suction side, then the water level. Hayward notes that suction air leaks show up as bubbles at the return jets.
How do I get an airlock out of my pool pump?
Refill the strainer pot, open the air relief valve on top of the filter, and start the pump while you stand clear. Close the valve when a steady stream of water, not air, comes out, as both the Hayward and Pentair manuals direct.
Why is my pool pump running but not pumping water?
Look for a clogged basket, an air leak, a closed valve, low water, or debris in the impeller. If the strainer pot stays empty while the motor runs, the pump has lost prime; turn it off right away so the seal does not burn up.
Does a pool pump have to be on a GFCI?
Yes. The Hayward and Pentair manuals both say to connect the pump only to a GFCI-protected branch circuit, in line with the National Electrical Code. Test the GFCI on a routine basis: press test and power should cut off, then press reset and power should return.