14 May 2026
Pool pump won’t start. You can hear the motor humming through the housing, but the impeller isn’t moving. Maybe you can spin the shaft by hand and the motor then runs fine until you switch it off, at which point it goes back to humming.
That’s a textbook failed capacitor. 90% of “pool pump won’t start” calls are capacitor faults. The remaining 10% are dead motors, jammed impellers, or a tripped thermal overload.
Pool pumps run long hours under load. Most run-of-the-mill motor run capacitors are rated for around 3,000-10,000 hours of operation. A pool pump running 8 hours a day chews through that in 1-3 years.
The motor itself is built to last 10-15 years if the windings stay cool and the bearings stay greased. So in 90% of failure cases, the motor’s fine. It’s the cap that wore out.
| Symptom | Probably capacitor | Probably motor |
|---|---|---|
| Humming, won’t start | ✓ very likely | only if cap is fine |
| Starts when you spin it | ✓ classic sign | - |
| Trips the breaker immediately | - | ✓ shorted winding |
| Burning smell | possible | ✓ likely |
| Visible black mark on motor casing | - | ✓ likely |
| Motor body unusually hot to touch after only a minute | possible | ✓ likely |
| Motor was rebuilt or replaced < 2 years ago | ✓ very likely cap | unlikely |
Most NZ pool pumps use a 25-50µF, 370V or 450V CBB60. Read the side of the existing cap; the spec is printed there. Match the µF on the label (within ±5%) and use equal-or-higher voltage. Browse the pool pump capacitors.
Capacitors are NZ$20-35. Motors are NZ$150-400 plus install. If the motor is also failed, weigh up whether to replace the whole pump (often cheaper than just the motor for residential gear) vs paying a pool tech for a motor swap.