Hot water element replacement: how to tell, and who is allowed to do it
A failed element and a thermostat that has drifted look identical from outside the cabinet: and the most commonly missed cause in Australia is not a fault at all.
A heating element is the electric component that actually heats the water inside a storage cylinder. And when one fails the usual result is no hot water at all from a tank that is otherwise full and undamaged.
Replacing it is one of the cheapest repairs available on a hot water system and is routine work for a licensed tradesperson. It is also, in Australia, not a job you do yourself. The element sits inside the electrical enclosure of a pressurised tank. And both halves of the work are licensed trades.
Most of the step-by-step guides that come up for this question are written for the United States. And they describe a job you are not permitted to do here. What is genuinely useful on this side, and worth doing first, is working out whether the element is even the problem, because several very different faults present as exactly the same symptom.
How do you know it is the element and not the thermostat?
From outside the cabinet, you largely cannot: and that is the honest answer. The element, the thermostat and the energy cut-out all sit behind the same cover plate. And a failure of any of them produces “no hot water”. What you can do is narrow it down by what else is happening, which is the information a plumber actually wants when you ring.
| What you observe | What it tends to point at |
|---|---|
| No hot water at all, and the safety switch or circuit breaker trips when the system is switched on | Strongly suggests an element that has failed to earth. When the metal sheath is breached, current leaks into the water and the tank, and the safety switch does its job. This is the one pattern that points fairly specifically at the element |
| No hot water at all, nothing trips, tank is full | An element that has burnt out open-circuit, a failed thermostat, a tripped energy cut-out, or no power reaching the unit at all. These cannot be separated from outside |
| Hot water runs out much faster than it used to, or never gets properly hot | Thermostat drift, heavy scale on the element, or (on a tank with more than one element) one of them having failed while the other carries on |
| Rumbling, popping or kettling noises from the tank | Scale built up on the element surface. The element overheats under the deposit, which is what eventually kills it |
| No hot water, nothing tripped, and it has been fine for years | Check the tariff before anything else. See below. This is the most commonly missed cause in Australia, and it is not a fault at all |
How many elements your tank has depends on the model. So the data plate on the unit and the owner’s manual are the reference rather than a general rule. If the symptom is lukewarm rather than cold, it is worth reading why hot water comes through lukewarm first. That one is very often not the element and not even the tank.
The Australian cause that is not a fault at all
A great many electric storage systems in Australia are wired to a controlled load: an off-peak tariff that energises the hot water circuit only during set hours, usually overnight. It is a large part of why an electric tank is cheap to run, and it is also why a perfectly healthy system can produce a cold shower.
Maybe the household has been using more hot water than usual, or the off-peak supply was interrupted. Or the circuit was switched off at the switchboard and never switched back on. In each case the tank simply has not been heated. Nothing is broken.
Before anyone opens anything, it is worth establishing whether the system is on a controlled load, whether that circuit is on at the switchboard. And whether the tank has had a chance to recover. A tradesperson called out to a tank that was switched off is an expensive way to learn this.
Why is replacing an element not a DIY job here?
Two reasons, and they stack.
The first is regulatory. Work on a hot water system is licensed plumbing work in every Australian state and territory. And the electrical side (the fixed wiring supplying the appliance) is licensed electrical work. An element replacement sits across both. Which licences and which paperwork apply is set by the regulator in your own state or territory. And where the line falls between what you may and may not touch is set out in full on the licensed work pillar.
The second is physical. Getting an element out means isolating the supply, draining a pressurised vessel full of water hot enough to scald badly, and breaking into a sealed tank.
An element that has sat in hot, mineral-laden water for a decade is frequently seized. And freeing it can damage the fitting or the tank lining. Turning a small repair into a replacement system. Refilling, purging the air and bringing the system back up to pressure properly is part of the job rather than an afterthought.
There is a third, quieter reason: the manufacturer’s warranty. An unlicensed repair on a cylinder is one of the standard grounds for losing it, which is covered in what actually voids a hot water warranty.
Is a new element worth it, or is the tank finished?
On a sound cylinder with years of life ahead of it, replacing an element is straightforwardly good value. It is among the least expensive components in the system, and the labour is a small fraction of a replacement unit. The real question is whether the cylinder is sound, and that is where the decision actually lives.
The useful thing to understand is that an element rarely dies for no reason. Heavy scale means the water chemistry is working against the appliance. A tank whose sacrificial anode has never been changed is a tank already corroding from the inside. And a new element buys time on a cylinder that is failing for an entirely different reason. So an element failing on an old, unserviced tank is often less a repair to authorise than a warning to act on.
The questions worth putting to the plumber, rather than asking for a number down the phone: what did the old element look like when it came out, is there heavy scale, has the anode ever been replaced and what condition is it in. And given the age of this cylinder is a new element money well spent or money spent late?
If the answer points at replacement, it is far better to have the comparison between system types while you still have options rather than in an emergency. How long a system should last is the other half of that judgement.
What is genuinely yours to do
- Check the switchboard. Confirm the hot water circuit is switched on and that nothing has tripped. This is outside the appliance and it is yours.
- Find out whether you are on a controlled load or off-peak tariff, and whether that supply has been interrupted. Your electricity bill or retailer will tell you.
- Note what happens when it is switched on. Does anything trip, immediately or after a while? That single observation is the most useful thing you can hand a tradesperson.
- Read the data plate on the unit for make, model and capacity, and find the manual if you have it. It tells the plumber what part to bring, which can save a second visit.
- Work out the age of the system and its service history. If you inherited it with the house and there is no paperwork, assume nothing has ever been serviced.
- Ask about the anode while the element is being changed, because the tank is already being worked on and that is the cheapest moment to find out.
Frequently asked questions
How do I know if my hot water element has failed?
You usually cannot tell from outside the cabinet, because the element, thermostat and energy cut-out all sit behind the same cover and any of them failing produces no hot water. The one pattern that points fairly specifically at the element is the safety switch or circuit breaker tripping when the system is switched on, which suggests the element sheath has been breached and current is leaking to earth. Noises like rumbling or popping suggest scale on the element, which is what usually kills it.
Can I replace a hot water element myself in Australia?
No. Work on a hot water system is licensed plumbing work in every Australian state and territory, and the fixed wiring supplying the unit is licensed electrical work, so an element replacement crosses both. Most of the step-by-step guides online are written for the United States and describe a job you are not permitted to do here. There is also the practical side: it means draining a pressurised tank of scalding water and opening a sealed cylinder, and a seized element can damage the tank fitting when it is freed.
Why does my hot water trip the safety switch?
Typically because the metal sheath of the element has been breached, so current is leaking into the water and the tank rather than staying in the circuit, and the safety switch is doing exactly what it exists to do. Leave the circuit switched off and call a licensed plumber or electrician. Repeatedly resetting it to get one more shower is the wrong response to that particular symptom.
I have no hot water but nothing seems broken. What else could it be?
Check the tariff before assuming a fault. Many electric storage systems in Australia run on a controlled load or off-peak tariff that energises the hot water circuit only for set hours, usually overnight. If that supply was interrupted, the circuit was switched off at the switchboard, or the household simply used more hot water than the tank could recover, you get a cold shower from a perfectly healthy system.
Is it worth replacing the element or should I replace the whole system?
On a sound cylinder with years left, replacing the element is good value, because it is one of the cheapest parts in the system. The judgement is really about the tank rather than the element. An element that failed under heavy scale, or one in a tank whose sacrificial anode has never been changed, is a signal that the cylinder itself is deteriorating, and a new element only buys time. Ask what the old element looked like and what condition the anode is in before deciding.
Why did my hot water element fail so soon?
The most common reason is scale. Mineral deposit builds up on the element surface, traps heat against it and makes it run far hotter than it was designed to, which shortens its life considerably. That is a water chemistry problem rather than a brand problem, and it is also why two identical tanks in different suburbs can behave very differently.
Does a continuous flow or instantaneous system have an element?
Electric continuous flow units do have heating elements, but the arrangement is different from a storage tank and there is no cylinder to drain. Gas continuous flow units heat with a burner and have no element at all. Either way the work is licensed, and on anything gas it is a licensed gasfitter rather than a plumber or an electrician.
Sources
What this page explains is based on these official sources. If you check one and it does not match what you read here, send it to us and the article gets corrected.
- Australian Government, energy.gov.au. Hot water systems — types, installation and energy performance
- Australian Building Codes Board. National Construction Code — Volume Three (Plumbing Code of Australia)