Fixing a Hot Water System That Has Stopped

The faults we see most

Failed element. Electric units. Water stays cold or goes lukewarm. In Perth, scale on the element is the usual accelerant — the coating traps heat against the element sheath and it burns out. Replacing it is routine, and it is worth checking the anode while the tank is open.

Failed thermostat. Also electric. Either no heating at all, or water that is scalding because the thermostat has stuck closed. The second one is the more urgent of the two.

Thermocouple or pilot assembly. Gas storage units. The pilot lights and then goes out when you release the knob. The thermocouple is a cheap part and a short job.

Relief valve. A temperature and pressure relief valve is meant to weep occasionally during a heating cycle. A valve that runs continuously is either failed or is telling you the mains pressure at your property is too high, which is a different fix — a pressure limiting valve at the meter.

Tempering valve. Bathroom water that has drifted too cool or too hot while the kitchen is unchanged.

Sacrificial anode consumed. Not a breakdown as such, but the thing that decides whether you get eight years or fourteen out of a cylinder.

What cannot be repaired

A leaking cylinder. If water is coming from the tank shell rather than from a fitting, valve or union, the steel has corroded through from the inside and no patch, sealant or weld is a legitimate repair. The unit needs replacing, and if it is leaking badly, it needs replacing today rather than next week — that is what emergency replacement is for.

We would rather tell you that on the phone than charge a call-out to confirm it.

Discoloured water

Brown or rusty water only on the hot side generally means corrosion inside the cylinder, and on an older tank that is an end-of-life indicator. Discoloured water on both hot and cold is more likely a mains issue or disturbed sediment in the street main after Water Corporation work nearby — worth ruling out before anyone blames the heater.

A rotten-egg smell on the hot side is a different thing again: it is usually a reaction between the anode and bacteria in the tank, and swapping to a different anode material often solves it.

Noises

Kettling, banging or popping when the unit heats is sediment. Water trapped under a scale layer flashes to steam and the layer cracks. On a tank that has never been drained in Perth's hard water, this is common and is a prompt to have the sediment flushed before the element goes.

A continuous flow unit that cycles on and off rapidly at low flow is usually hitting its minimum flow threshold rather than faulting — a common complaint when someone runs a bathroom tap barely open.

Before you call

Note the brand, the model number from the data plate, and roughly how old the unit is. Say whether it is gas or electric, tank or wall-mounted, and what exactly is happening — no hot water at all, or not enough, or a leak, or a noise. That five minutes decides which parts come on the truck and often saves a second visit.

If the unit turns out to be past saving, the installation page covers what replacing it involves and the cost guide sets out the ranges. For a leak that is not coming from the heater at all, try leak detection or burst pipes.