Water Heater Wiring & Electrical Faults
Water heaters are the single most common source of earth leakage in a home, for a reason that is built into what they are: a heating element sitting inside a tank of water, where a failure of the element is a failure directly into earth.
Why the earth-leakage breaker trips when the heater runs
When a heating element begins to fail, it lets a small current leak through the water to earth. That leakage is exactly what an earth-leakage breaker is designed to detect, so it disconnects — usually while the heater is running or shortly after it switches on. The breaker is not being oversensitive; it is detecting a genuine path to earth, and that path is the one a person in contact with the water would otherwise complete.
What safe water heater wiring looks like
A dedicated circuit rather than a spur off the sockets, earth-leakage protection on that circuit without exception, an isolator located outside the wet zone so the heater can be switched off without reaching into a bathroom, correct earth bonding, and connections in an enclosure rated for a humid environment. Any of these missing is worth correcting whether or not anything has tripped yet.
Symptoms worth acting on
The earth-leakage breaker trips whenever the heater is on
Hot water stops partway through a shower
Any tingle or shock from taps, pipework or the shower — stop using it and call now
Discolouration or scorching at the heater's connection point
No isolator switch, or one located inside the wet area
The heater shares a circuit with sockets or lighting
Frequently Asked Questions
Most often the element inside the heater rather than the wiring feeding it, though testing is what separates the two. It is worth knowing before replacing anything, because replacing a heater that had a wiring fault leaves you with the same trip and a new heater.
Treat it as an emergency. A tingle means current is finding a path through the water or the pipework, and the conditions that make it a tingle rather than a serious shock can change with something as ordinary as standing on a wet floor. Stop using the water, switch the heater off at its isolator if you can do so safely, and call 0564036091.
It should not. A water heater is a large continuous load and it needs its own protected circuit, both so it does not compete with other loads and so it can be isolated on its own when there is a fault — which, given how often the element is the fault, matters more here than for most appliances.
Outside the wet zone, accessible without reaching into a shower or over a bath. The point of an isolator is that it can be operated safely in exactly the situation where you most need to switch the heater off, and one mounted inside the wet area defeats that.