Stop and make it safe if
You smell gas: don't relight anything or flick switches nearby. Go outside and call your gas supplier's emergency line from there. If water is pouring from the tank or through a ceiling, close the cold water valve on the pipe going into the heater and switch the heater off at the switchboard (or turn its gas off). Never take the cover off an electric heater: the parts behind it carry mains power.
Know which system you have
The checks depend on the type. The label on the side of the unit names the brand and model, and usually the year it was made. Take a photo of it now: the plumber will ask.
Gas storage keeps a tank of water hot with a gas burner. Gas continuous flow has no tank and heats water as it passes through. Electric storage heats a tank with elements. A heat pump is electric too, using an air source heat pump to warm the tank. Solar heats water with the sun and uses a booster when the sun can't keep up.
Checks you can do safely
Run every hot tap
If the kitchen runs hot but the bathrooms are cold or lukewarm, the heater may be fine. Bathrooms are often fed through a tempering valve, and a faulty one can cut the hot supply to them alone.
Check the switchboard
Electric storage systems, heat pumps and gas continuous flow units all need power. Look for a tripped switch labelled hot water and reset it once. If it trips again, leave it off and call a plumber: repeated tripping points to an electrical fault.
Think about off-peak
Many electric tanks only heat overnight, on an off-peak tariff. If the house has used a lot of hot water today, the tank may simply be empty until it reheats tonight.
Check the gas
Try the cooktop or another gas appliance. If nothing gas works, the problem is the supply, not the heater. Check the valve at the meter is open, or that the gas bottles aren't empty.
Look at the pilot on a gas tank
Older gas storage systems have a small pilot flame behind a window. If it's out, relight it exactly as the label says. If it won't stay lit after a second try, stop.
Write down any error code
Continuous flow units and heat pumps show a code on the unit or the controller when something is wrong. Note it down. It tells the plumber where to start, and which parts to bring.
Signs it's time to call a plumber
- Water pooling under the tank, or rust stains down its side.
- The relief valve on top keeps running, not just the odd drip.
- The switch trips again after one reset.
- The pilot keeps going out, or you can smell gas.
- Water that comes out rusty, smelly or full of grit.
- Hot water that runs out much sooner than it used to.
- An error code that keeps coming back after a restart.
Repair or replace?
A plumber will check the age of the system, the condition of the tank and whether the faulty part is still available. Thermostats, elements, valves and igniters can often be swapped. When the tank itself is leaking, expect the plumber to talk about replacement instead.
In Victoria, there's a rule to know about. From 1 March 2027, when a gas hot water system in an existing home reaches the end of its life, it has to be replaced with an efficient electric one, like a heat pump. A working gas system can stay, and the Premier's announcement says gas systems "can still be repaired if they break down". Read our page on Victoria's gas hot water rule and check the current rules before you decide.
If it does need replacing
A replacement isn't just a swap of boxes. Depending on your state, the new system may need a tempering valve on the bathroom supply: the rules differ, and our guide to hot water temperature and scalds sets them out state by state.
In Queensland, heat pump and solar systems "must be installed by a hot water installer" holding a QBCC solar and heat pump endorsement. In Western Australia, installing or replacing a water heater isn't counted as minor work, so the plumber owes you a certificate of compliance afterwards. Our compliance certificates guide covers the other states.
Have this ready when you call
- The type of system, and the brand and model from the label.
- Roughly how old it is.
- What you've already checked, and what happened.
- Any error code, written down exactly.
- Photos of the label, the valves and any leak.
Questions to ask the plumber
- Can it be repaired, and is the part in stock?
- Is the tank itself sound, or is it starting to fail?
- If it's replaced, does my state require a tempering valve this time?
- Will I get a compliance certificate, or a record of the work?
- If it's gas and I'm in Victoria, what are my electric options?
What we would do
Do the switchboard and gas checks once each, then stop. Resetting a breaker over and over, or relighting a pilot that won't hold, doesn't fix a fault: it just hides it until something gives. Call with the label photo and the error code in hand, and ask about repair first. A good hot water plumber will tell you plainly when a repair isn't worth it.