A Henderson homeowner called: no hot water. We’d installed the cylinder ourselves about three years earlier, so we went out the same morning.
The cylinder was fine. The fault was on the electrical side.
Why “no hot water” often isn’t the cylinder
When the hot water stops, most people assume the cylinder has failed. Often it hasn’t — it simply isn’t getting power.
A hot water cylinder runs on its own dedicated circuit, and in a lot of Auckland homes that circuit is switched by the lines company rather than being live all day. That means there are several places outside the cylinder where the heating can stop: the breaker at the switchboard, the control relay, or the wiring between them.
The pattern we see most is a house that has had electrical work done recently. A meter upgrade or switchboard change involves disconnecting and reconnecting circuits, and the hot water circuit is an easy one to leave off or reconnect to the wrong control. Everything else in the house works perfectly, so nobody links the two — until a couple of days later when the hot water runs out.
The rule of thumb
If the cylinder is only a few years old, check the power before you assume the cylinder has failed.
Cylinders do fail — elements burn out, thermostats stop working, old tanks corrode — but a relatively new cylinder that suddenly gives you nothing is much more likely to be an electrical supply problem than a tank problem. It’s also the cheaper thing to rule out first.
Worth checking before you call anyone:
- Has any electrical work been done recently — a meter upgrade, a new switchboard, solar, an EV charger?
- Is the hot water breaker at the switchboard on?
- Is the water stone cold, or lukewarm? Stone cold usually points at supply; lukewarm often points at the cylinder itself.
Who fixes what
Plumbers own the cylinder and the pipework. Electricians own the supply to it. We’ll tell you honestly which side of that line your problem is on rather than replacing a cylinder that was never broken.
If you’re in Henderson or anywhere in West Auckland and your hot water has stopped, give us a call — we’ll work out what’s actually wrong first.
Common questions
How long should a hot water cylinder last?
Many give 15 to 20 years, and some go longer. That’s why a cylinder only a few years old suddenly producing nothing is more likely to be a supply problem than a failed tank.
My water is lukewarm rather than cold. What does that mean?
Lukewarm usually points at the cylinder or its controls — a failed element in a two-element cylinder, a thermostat problem, or hot water being used faster than it can recover. Stone cold more often means the cylinder isn’t getting power at all.
Can an element or thermostat be replaced, or do I need a whole new cylinder?
They’re replaceable parts, and on a sound cylinder that’s usually the right repair. Replacing the whole cylinder makes sense when the tank itself is leaking or has reached the end of its life.
Why would recent electrical work stop my hot water?
A meter upgrade, switchboard replacement, solar install or EV charger all involve disconnecting and reconnecting circuits. The hot water circuit is easy to leave off or to reconnect to the wrong control, and because everything else in the house works nobody links the two until the hot water runs out days later.
Should I call a plumber or an electrician?
Call us and we’ll work out which it is. We own the cylinder and the pipework, electricians own the supply — and we’d rather tell you it’s an electrical fault than replace a cylinder that was never broken.