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).
Davey pressure pumps are a Kiwi staple on tank, bore, and rainwater systems. When one hums but won’t start, trips the breaker on switch-on, or cuts out under load, a failed run capacitor is a very common culprit — and an affordable DIY fix if you take the right precautions. This guide covers the popular Davey XP and Torrium families.
How a Davey capacitor fails
The run capacitor gives the single-phase motor the phase shift it needs to start and keep turning. As it ages — accelerated by heat and the constant start-stop cycling of a pressure system — its capacitance drifts or it fails outright. Typical symptoms:
- Motor hums but doesn’t spin (then trips on thermal overload)
- Slow or laboured start-up
- Breaker trips the instant the pump tries to start
- A bulged, domed, leaking, or swollen capacitor can
On a Torrium or Torrium 2 unit the motor electronics sit under the controller; on XP models the capacitor is usually in a housing on the motor body.
Safety first
- Isolate the power at the breaker or isolator before opening anything, and confirm the pump is dead.
- A capacitor holds a dangerous charge even when unplugged. You must discharge it before touching the terminals (Step 4).
- In NZ, fixed mains wiring is the work of a licensed electrician. If your Davey is hard-wired into a supply rather than on a plug and lead, or you’re unsure, get a sparky.
Match the value — don’t guess from the model
Davey run capacitors vary across the XP and Torrium range; values are commonly in the low tens of microfarads with a voltage rating of 400–450V AC, but ranges differ by motor size. Never fit a cap based on the model name alone. Read the µF and voltage printed on your old capacitor or on the motor nameplate, and match the µF exactly while meeting or exceeding the voltage rating. The wrong capacitance will overheat and ruin the windings.
Unsure how to read the markings? The find-your-capacitor wizard decodes them for you.
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.