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.
Steps
1. Isolate the power
At the breaker/isolator and unplug the pump if it’s on a lead. Verify it’s dead before continuing.
2. Remove the capacitor cover
On XP units it’s the housing on the motor; on Torrium units lift the controller cover. Photograph the wiring first.
3. Locate the capacitor
— a cylindrical can with two or more spade terminals.
4. Discharge it
Bridge the 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 to drain the stored charge. Do this every time.
5. Photograph and remove the leads
Noting which connector goes to which terminal.
6. Read the old capacitor
Record the µF and voltage, then source an exact µF match at equal or higher voltage.
7. Fit the new capacitor
Into the same clamp/bracket and push the spade connectors firmly home on the matching terminals.
8. Refit the cover
Check nothing is pinched or loose, and confirm the area is dry.
9. Restore power and test
The pump should start crisply and build pressure smoothly. If it still hums, switch off and investigate further.
If a new capacitor doesn’t fix it
A correctly-matched cap that doesn’t solve the problem points elsewhere: a seized pump bearing, a failed pressure switch or Torrium controller, a tripped thermal overload, or a worn motor winding. On Torrium models the electronic controller itself can fail and mimic a capacitor fault. If in doubt, have a pump technician or electrician test the motor.
Get the right Davey capacitor
See our full pump capacitors range or go straight to the well & pressure-pump selection. Not sure which one? Run the find-your-capacitor wizard and match your old cap in a minute. Browse all Davey pump capacitors by model to match your exact unit.
Capacitors are shipped tracked, around 2 weeks via NZ Post or courier, prices in NZD incl GST, backed by a 90-day DOA guarantee.
NZ-owned. NZD incl GST. 90-day DOA guarantee.