Time: 20–30 minutes. Skill: homeowner-comfortable with a screwdriver and able to isolate the circuit at the breaker. Cost: the price of one replacement capacitor (NZD incl GST).
A Waterco Hydrostar that hums but won’t start
Waterco’s Hydrostar is a popular choice on New Zealand pools, built to push plenty of water through the filter day in, day out. That steady duty is exactly what wears a capacitor down over time. The tell-tale sign of a failing Hydrostar capacitor is a pump that hums or buzzes when you switch it on but doesn’t turn — or one that needs a hand-spin of the rear fan to get going. You might also notice it tripping the breaker shortly after start-up. Before assuming the motor is toast, suspect the capacitor: it’s an inexpensive part and a very doable home repair.
Get the safety steps right and you can have the Hydrostar back in service the same afternoon.
Make it safe before you start
A capacitor stores a dangerous charge even with the pump switched off and unplugged. Never skip these steps.
- Isolate the power at the breaker or the pump’s isolator switch — the pump’s own button is not enough.
- Discharge the capacitor by bridging its terminals with a bleed resistor (around 10–20 kΩ, 5 W) or a proper capacitor discharge tool — a bare insulated-handle screwdriver across the terminals also drains it but sparks violently and can pit the terminals, so use that only as a last resort before touching any wiring, to release the stored charge.
- New Zealand law requires a licensed electrician for fixed mains wiring. If the Hydrostar is hard-wired or you’re unsure at any point, call a registered sparky.
Where the capacitor sits on a Hydrostar
On Waterco Hydrostar motors the capacitor is typically housed under a cover on top of the motor or within the rear terminal box near the wiring connections. Lift or unscrew the cover and you’ll find the cylindrical can clamped in place with spade connectors. On some builds it’s tucked close to the terminal block, so note the layout before disconnecting anything.
What you’ll need
- The replacement run capacitor — match the µF (within ±5%) and equal-or-higher voltage to the one fitted now.
- Phillips and flat screwdrivers.
- An insulated screwdriver, or a 10–20 kΩ bleed resistor with insulated leads, to discharge the old capacitor safely.
- A multimeter, if you want to confirm the diagnosis before swapping.
- Your phone — to photograph the wiring before disconnecting anything.
Steps
1. Isolate the supply
At the breaker/isolator, then try to start the pump to confirm it’s dead.
2. Discharge the capacitor
— wait a minute, then short across the terminals with a bleed resistor or a proper discharge tool (a bare insulated screwdriver also works but sparks — last resort) to drain any stored charge.
3. Open the cover or terminal box
To expose the capacitor and its clamp.
4. Photograph the wiring
And terminal positions for an easy, accurate reassembly.
5. Read the old capacitor’s markings
— record the printed µF and voltage. Many single-phase pool pumps sit in the rough 20–50µF range at around 450V, but confirm from your own capacitor or the motor nameplate — the wrong µF can damage the motor.
6. Remove the old capacitor
— release the clamp and gently unplug the spade connectors.
7. Fit the new capacitor
With matching µF and voltage, pressing each spade firmly onto the right terminal, then re-secure the clamp.
8. Refit the cover/terminal box
And check no wires are trapped and the fan spins freely.
9. Restore power and test
— switch on; the Hydrostar should start cleanly and run steadily. If it still hums, isolate again and recheck the connections.
Choosing the right Waterco capacitor
Match three things: the µF value, the voltage rating, and the can size/terminal type. A higher voltage rating is fine, but never change the microfarads. If your old cap is readable, copy its numbers exactly; if it’s burst or faded, use the motor nameplate or our find-your-capacitor wizard. See compatible parts in our pump capacitor range or the pool capacitor shop. Browse all Waterco pump capacitors by model to match your exact unit.
Hydrostar-specific tips
- The rear terminal box can collect moisture in damp pump sheds — wipe it dry and check for corroded spades while you’re in there.
- Re-seal the cover properly so the new capacitor stays dry; moisture is a common repeat-failure cause.
- If the shaft won’t turn by hand with the cap removed, suspect a bearing rather than the capacitor.
Find your Waterco capacitor and order
Unsure of the rating? Our find-your-capacitor wizard makes it painless, or jump straight to the pool capacitor shop or the full pump capacitor range.
Every order ships tracked, around 2 weeks via NZ Post or courier, prices in NZD incl GST, backed by a 90-day DOA guarantee. Proudly NZ-owned.