Pool pump motor capacitor exposed for replacement on a daylight equipment pad

How To Find the Correct Capacitor For Your Pool Pump Motor

A pool pump motor that hums on startup but doesn’t spin is almost always a failed capacitor. It’s a $30–$150 part and a 15-minute swap, but only if you order the right one. There’s no universal pool capacitor — the wrong microfarad rating won’t start your motor and can damage the windings. Here’s how to identify and order the correct replacement.

What does a pool pump capacitor actually do?

Single-phase induction motors need a phase-shifted current pulse to start spinning. The capacitor stores and releases that pulse during the first split-second of operation. Once the motor is up to speed, a centrifugal switch disconnects the capacitor (in start-only designs) or it continues to run alongside the motor (in run capacitors). When the capacitor degrades, the motor can’t generate startup torque — you hear it hum, but it won’t turn.

The two specs that define a capacitor

  1. Microfarad rating (μF or MFD) — the storage capacity. Common pool pump values are 25, 30, 35, 50, and 70 MFD.
  2. Voltage rating — usually 250V, 370V, or 440V. Higher is always OK; lower is not.

Both numbers are printed on the side of the existing capacitor. Match the microfarad exactly; you can substitute up the voltage rating but never down.

Discharge before touching. Capacitors store energy even when the pump is unplugged. Always discharge by shorting the two terminals with an insulated-handle screwdriver before handling. A charged 370V capacitor can give you a memorable shock.

Where to find the spec on your existing capacitor

Pop the back cover off the motor (usually 2–4 screws). The capacitor is a cylindrical canister, typically 2–3 inches tall, with two terminals on top. The microfarad and voltage are stamped or printed on the side — sometimes a sticker, sometimes embossed. Take a clear photo before pulling it.

If the existing capacitor is so old the label has worn off, look up the motor model number on the motor’s data plate. Every major manufacturer publishes a parts breakdown that lists the correct capacitor by motor model.

Run vs. start capacitor

Most residential pool pumps use a single “start” capacitor that engages only during startup. Some larger pumps and most two-speed designs also have a “run” capacitor that operates continuously. If your motor has two capacitors, replace both at the same time — the one that hasn’t failed yet is usually within a year of doing so.

Popular pool pump capacitors in stock

Match the microfarad rating on your existing capacitor to one of these:

Jandy Pro Series 25 MFD 370V motor run capacitor for pool pump

Jandy 25 MFD / 370V Run Capacitor

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Jandy Pro Series 30 MFD 370V motor run capacitor for pool pump

Jandy 30 MFD / 370V Run Capacitor

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Jandy Pro Series 50 MFD 370V motor run capacitor for pool pump

Jandy 50 MFD / 370V Run Capacitor

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30 microfarad EMG motor pool pump capacitor

EMG 30 μF Motor Capacitor

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How to swap the capacitor (the easy part)

  1. Cut power at the breaker. Verify with a non-contact voltage tester at the motor leads.
  2. Remove the back capacitor cover (2–4 screws).
  3. Discharge the old capacitor by shorting its terminals with an insulated screwdriver.
  4. Photograph the wires before disconnecting so you know which spade terminal goes back where.
  5. Pull the spade connectors, remove the old capacitor (usually a single retaining clip or strap), drop the new one in, reconnect the spades, and reinstall the cover.
  6. Restore power and test.
If the motor still hums after a new capacitor: the centrifugal switch may be stuck, the bearings may have seized, or the windings may have shorted. New capacitor + same hum = the motor itself is likely done. See our replacement pool pump motor guide.

Need help matching a capacitor to your motor? Send PST Pool Supplies the motor data plate and a photo of the existing capacitor, and we’ll match the exact rating — usually same day.

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