A water heater mixes the two things a house most needs kept apart: mains electricity and the water you stand in. Installed and maintained properly, the safety chain has three independent links — earthing, the ELCB, and the thermostat — and all three must fail before anyone gets hurt. The point of this guide is to make sure yours have not quietly failed already.
The three-minute monthly check
- Press the ELCB test button on your distribution board. It must trip instantly with a firm clack. An ELCB that hesitates or holds is a dead safety device — replace it before anything else in this article matters.
- Look at the heater isolator switch (the big switch outside the bathroom). Discolouration or a warm faceplate means a loose connection cooking behind it.
- Watch the shower behaviour. Any tingle, however faint, is current finding a path through you. Switch the unit off at the isolator and stop using it — a tingle is never normal and never "just static".
Twice a year for storage tanks
Lift the pressure relief valve lever until water flows, then release. If nothing flows, or it drips constantly afterwards, the valve needs replacing — it is the only device standing between a stuck thermostat and a pressurised tank of scalding water. While you are there, check the drip from the valve outlet pipe: an occasional drip during heating is normal, a steady stream is not.
Signs that mean switch it off today
- Any electrical tingle from taps, shower head or the water stream
- The heater trips the ELCB, even occasionally — that is leakage current, and it is telling you something
- Rust streaks or bulging on a storage tank casing
- Burning smell or crackling from the unit or isolator
- An instant heater that cycles hot-cold-hot — often a failing flow sensor overdriving the element
The installation shortcuts to ask about
If your heater was installed cheaply, two questions expose the common shortcuts. First: "does it have its own dedicated circuit and ELCB?" A heater spliced off a socket circuit shares its protection with whatever else trips that line. Second: "where is the earth connected?" An unearthed heater works perfectly — until the day the element casing cracks. Neither shortcut is visible from the bathroom, which is why they survive for years.
Our water heater service includes a wiring and earthing check with every installation and every service visit, and we will show you the test readings rather than asking you to take our word for it.