Why does my hot water keep tripping the safety switch?

What the safety switch is telling you

A safety switch cuts the power within milliseconds when it detects electricity leaking to earth, to protect you from a shock. If it trips every time the hot water circuit is on, the fault is usually in the hot water system itself, not the switchboard.

The common causes

A failed heating element

This is the most common cause. When an element's outer sheath cracks or corrodes, water reaches the live coil inside and the safety switch trips. It often happens the moment the element starts heating, so on an off-peak tariff you may notice the power tripping at night, when the off-peak circuit switches on.

Water in the electrical compartment

A leaking valve or fitting above the element cover, rain getting into an outdoor unit with a damaged cover, or heavy condensation can all bring water into contact with the wiring. Check for drips or rust around the cover, but don't take the cover off.

A thermostat or wiring fault

Thermostats and terminals can fail or burn out over time. On the Sunshine Coast, ants and other insects sometimes nest behind the element cover and cause a fault.

Storms and power surges

Lightning and power surges can damage elements, thermostats and the control boards on heat pumps. If the tripping started after a storm, mention that when you call.

Heat pump and solar faults

On a heat pump, a failed fan motor, compressor or control board can trip the circuit. On a solar system, the electric booster element can fail in the same way as a standard tank.

What you can safely do

1. Switch off the hot water circuit at the switchboard, or the isolator near the unit, and leave it off.
2. Look for water on or around the system. If it's leaking, turn off the cold water valve going into it.
3. Don't keep resetting the safety switch. Once is enough to see if it trips again.
4. If other circuits are tripping too, the problem may be elsewhere in the house, so call an electrician.

Our guide on how to turn off a hot water system shows where the valve and isolator usually are.

Repair or replace?

A failed element or thermostat is usually a straightforward repair if the tank is sound. If water is getting into the electrical parts because the tank itself is leaking, or the system is well past its typical life, replacing it is usually better value. Our repair or replace guide explains how to decide.

Who can fix it

Electrical work on a water heater must be done by a licensed electrician, or a plumber who holds a restricted electrical licence for water heaters. Justin holds Restricted Electrical Work Licence 1508073 for water heaters, as well as his QBCC plumbing licence. See electric hot water and hot water repairs.