Published 2026-10-22 by 24hr Electrician Sydney
You turn on the shower and the water is cold, or you find the safety switch off first thing in the morning. An electric hot water system that trips the power is a common problem in St George homes, and it is often discovered first thing in the morning, because many systems heat overnight on an off-peak or controlled load tariff.
How electric hot water works
An electric storage system heats water in an insulated tank with one or two heating elements. A thermostat switches the element on and off to keep the water at temperature. Many systems are on a separate circuit with their own breaker, and on a controlled load tariff the network only supplies that circuit at set times, usually overnight. That is why a fault often only shows up when the heating cycle starts.
Common causes
- A failed heating element
- Water getting into the element or thermostat cover
- A faulty thermostat
- Damaged wiring to the unit
- A corroded or loose connection at the isolator switch next to the tank
Heating elements sit inside the water. When one fails, water can reach the live parts and current leaks to earth, which is exactly what a safety switch is designed to catch.
Signs to look for
- The safety switch trips at the same time each night or morning
- The hot water breaker trips when you turn it back on
- Water dripping from the cover plates on the side of the tank
- Rust stains on the tank or the floor around it
- Water that is lukewarm rather than hot
Repair or replace?
If the tank isn't leaking, an element or thermostat replacement is often enough. If the tank is leaking, replacement is the only option.
The age of the system matters too. If an older tank needs a new element and is showing rust, it may be better to plan a replacement rather than repair it now and again in a year. Replacing a hot water system involves a licensed plumber for the water connections and an electrician for the electrical side. We can do the electrical testing and repairs and work with your plumber on a replacement.
What to do now
Leave the hot water circuit off and call 0421 772 661. We'll test it and tell you the best option.
- Turn off the hot water breaker or isolator, then reset the main safety switch so the rest of the house has power
- Don't keep switching the hot water circuit back on to see if it holds
- Don't remove the cover plates on the tank, as there are live parts behind them
- If water is leaking near the electrics, keep clear of it
What we test
We isolate the system and test the element, thermostat, wiring and isolator. An insulation resistance test shows whether the element is leaking to earth. We also check the circuit back to the switchboard, so we know the fault is in the tank and not the cable. Read more about our fault finding service.
Thinking about a heat pump?
If your tank is due for replacement, it is worth looking at a heat pump system. Heat pumps use much less electricity than a standard element to heat the same water. They need a suitable spot outside for airflow and an appropriate electrical supply, which we can check for you.
Other appliances that trip safety switches
If the hot water tests fine, the cause may be elsewhere. Fridges, washing machines, ovens and outdoor equipment can all trip a safety switch. The same rule applies: isolate the circuit, and get it tested rather than resetting it over and over.
Cold shower and a tripped safety switch? Call 0421 772 661, 24 hours a day.