Water Heater Overheating? 6 Simple Fixes6 min read

In the fabric of modern living, water heaters have become a household staple; I, for one, couldn’t imagine living without mine. But they’re not immune to problems, and your water heater overheating can be a genuine hazard, bringing to mind the horrors of fire hazards or even explosions.

The key lies in paying attention to the small signals your appliances are sending you, including your water heater, along with taking swift action when you think something is wrong. With some maintenance, you can have a safe, warm, comfortable home that works for everyone.

I’ll take you through the main things to look out for, the signs you should pay attention to, and the preventative measures you can take to stay safe.

Ever heard of AI content? It’s common, but not on BuildFanatic! We value accuracy, so Mark Longhurst, a seasoned plumber with 15+ years of experience and owner of Pipesmart, has expertly reviewed this article. Look for his quotes throughout.

What Causes a Water Heater to Overheat?

There are a few reasons your water heater might overheat. Here are the usual suspects that I’ve come across:

Sediment Buildup

I’ve talked about this before, but sediment buildup (of minerals like calcium and magnesium) can build up at the water heater. Depending on where you live, you may have a lot of these minerals to contend with. They’re not normally harmful to your health, but they can cause a bit of chaos in your water-based appliances.

Over time, this sediment can build up at the bottom of the water heater tank. This essentially insulates the heating element, causing it to get really hot. If you’ve just moved into an old house (as we did), you might find that you have an old water heater to go along with it.

Thermostat Malfunction

The thermostat inside a water heater regulates the temperature of the water. It’s an obvious cause, but if this isn’t working, it may not recognize when the water hits the proper temperature, causing it to get way too hot.

High Water Pressure

Sometimes, high water pressure can cause overheating, too: the speed of the heating process may cause the water heater to overdo it.

This can be caused by a few things, although frustratingly, some of them can’t be prevented by you:

  • Excessive water pressure from the district or city main water supply – there’s not a lot you can do about this, annoyingly
  • Faulty pressure relief valve (a safety feature which is designed to release excess pressure – sometimes if this is set wrong, it can operate wrongly, causing pressure to build)
  • Trapped air in your water pipes – water pipes are designed to deal with large volumes of liquid, but air trapped in there can cause sudden bursts of pressure
  • Location – being near a fire hydrant, which uses a huge amount of water pressure, can impact your water pressure, too

Fluctuations in Voltage

Voltage can cause problems, too. For example:

  • Faulty boiler – this can cause the water to continually heat beyond the set temperature
  • Thermostat issue – the thermostat regulates the temperature, and so of course, if it fails, the water can overheat
  • Circuit wiring problems – if there is any faulty wiring, like loose connections or damaged insulation, this can cause to electrical problems including overheating
  • Short circuit – this can happen when an unintended connection is made between electrical components. This can cause problems with water heaters like disrupting the function of the heating element or the thermostat
  • Grounding issues – proper grounding is crucial to keep all electrical appliances safe, and grounding issues can cause issues with overheating

Lack of Maintenance

I know that this sounds like a kind of boring task, but regularly checking your water heater for small problems can stop them turning into bigger issues later on.

Signs Your Water Heater is Overheating

How can you tell if a water heater is overheating? In my experience, there are a few tell-tale signs:

Lukewarm Water

This sounds a little odd, but bear with me. When water heaters overheat, the thermostat fails to regulate the temperature, and the water will get too hot.

But this can trigger the pressure relief valve, and then some of the hot water is released and replaced by cold water. So you might be running the hot faucet, only to find that it just won’t heat up properly. Sounds counterintuitive, but it’s true. So if your bath isn’t heating up the way it should, that might be a clue.

Rumbling, Whistling, or Popping Sounds

Such an obvious clue, but if you hear strange rumbling, popping, or even high-pitched whistling sounds, it can mean the water is boiling and therefore the tank is overheating.

I always say weird noises are your appliances’ way of telling you there’s a problem. From banging dryers to humming garbage disposals, if you hear a weird sound, chances are that something’s up.


If you have leaks around the water heater, this could be caused by overheating, which can make the pressure relief valve fail.

What should you do about your overheating water heater?

Okay. I’ve gone through the scary part. What about solutions?

I’d say that if you’ve noticed your water heater overheating, it’s time to call a professional. A plumber can diagnose and fix the problem.

If you’re wondering what might happen, here’s what I would say is the most common practice: they will inspect the thermostat, check the heating element, inspect the pressure relief valve and tank, and check the water supply. After that, they’ll let you know what needs to happen next to fix the problem.

how to prevent your water heater from overheating

It sucks to have to deal with problems with your water heater – I know from experience that it can be expensive. I always say with stuff like this that prevention is better than cure. Here are a few things you can do to reduce the chances of this happening again:

Check the Thermostat

The thermostat can often be the culprit, I have found, so it’s best to keep an eye on it. Make sure the temperature is set to the recommended level by the manufacturer. Most manufacturers recommend a temperature between 120°F (49°C) and 140°F (60°C).

Check on the Pressure Relief Valve

The pressure relief valve is super important, as it releases pressure when it reaches a certain level. Checking on this every now and then to make sure it’s working properly is a good call.

Check on the Heating Element

The heating element, if not functioning properly, can cause the water heater to overheat. You can replace the heating element if necessary.

I usually calibrate the water heater to make sure it’s set at the right temperature (usually 120°F (48.9°C) and 140°F (60°C). This prevents overheating and makes sure that the water is both warm and safe for domestic use. I use a programmable thermostat for this, as it gives more precise control.

Mark Longhurst

Flush the Tank Annually

I find this to be a kind of satisfying job. Sediment buildup can cause problems, so regular flushing of the tank can remove the worst of it.

Insulate the Tank

This sounds weird, but it can work. Insulating your water heater tank can prevent heat loss, which stops the water heater from overheating to compensate.

How do you do this? The simplest way is to use an insulating blanket kit. Always follow the instructions, and make sure you switch off the water and the power to the water heater before you begin.

Regular Maintenance

A licensed plumber can come check on your water heater every now and then, which means they can catch issues early.

Personally, I’d recommend a regular maintenance checkup for your water heater at least once a year. A plumber can flush the tank, test the pressure relief valve, and identify any problems before they escalate. You can also ask them to perform a preventative maintenance schedule (PMS) for your heating system. An investment, but could save you money, time, and stress in the long run.

Mark Longhurst

The Dangers of an Overheating Water Heater

I want to say up front not to panic: an overheating water heater is a problem, but a professional can fix it for you if you don’t feel confident. I do know from experience how stressful this can be, but it’s best not to ignore it and deal with it asap.

There are a few major risks of an overheating water heater, including:

  • Burning hazard – if the water temperature exceeds safe limits it can result in scalding, burns, and can be a real risk for everyone including the children and the elderly
  • Pressure buildup – the increased pressure can cause a risk of burns and potential damage to the area surrounding your water heater
  • Tank failure – the ongoing heat can cause issues with the structural integrity of the water heater tank, which can lead to tank failure, leaks, and even water damage to your property
  • Electrical hazards – overheating can cause stress to the electrical components, increasing the risk of electrical fires
  • Reduced appliance lifespan – your water heater can’t handle overheating forever, and you will probably need to replace or repair it earlier
  • Explosion – this is the worst-case scenario, obviously, but if the pressure relief valve fails and pressure builds to dangerous levels, this can lead to an explosion.

Replacing a Faulty Water Heater

Sometimes, it’s time to call it quits. If your water heater is damaged beyond repair, it might be time for a new one. A professional can tell you if it’s time.

If you’re in the market for a new water heater, there are a few types to choose from:

  • Conventional storage-tank water heaters – these store water in a large tank, and are the most common type
  • Tankless water heaters – these heat water on demand, reducing the need for a tank
  • Heat pump water heaters – these use electricity to move heat from one place to another, rather than generating heat directly
  • Solar water heaters – these use solar energy to heat water
  • Hybrid water heaters – these use a combo of methods to heat your water at home

Installing a new water heater is absolutely not a DIY project. You’ll need a professional plumber, someone who is licensed, insured, and has good reviews and references. If you meet with a plumber and you don’t feel comfortable, don’t hire them: this is a really important job, and a rogue plumber can compromise your safety.

Water Heater Overheating: Key Takeaways

There are a few reasons why your water heater is overheating. The solutions are pretty simple:

  • Check the thermostat – this is a likely culprit in my experience
  • Check on the pressure relief valve – a damaged valve can cause problems with pressure building and overheating
  • Check on the heating element – if the heating element is broken, it can cause the water to get really hot
  • Flush the tank at least once a year – this gets rid of all the minerals/sludge that can build up in your tank
  • Insulate the tank – essentially wrapping a tank in a special blanket, this can help your water heater to reach the correct temperature without losing heat
  • Regular maintenance – book a regular maintenance check with a licensed plumber to catch problems before they start

I’ve been there with an overheating water heater, and I know how stressful it is. But most of the time, a licensed plumber can fix it quickly. As always – as boring as it sounds – I think maintenance is key. Catch problems early if you can; it’s way better than trying to fix huge problems later down the line!

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Hi, I'm Ed, and I run BuildFanatic! I enjoy providing the best possible information on a range of home improvement topics.

Mark Longhurst
Plumber at http://www.pipesmart.com.au/ | Website | + posts

Mark Longhurst is a professional plumber with over 15 years of experience, owns Pipesmart, and is our resident expert in all things plumbing.

Mark helps review plumbing-related articles for BuildFanatic to ensure we're providing our readers with the most accurate and updated advice.

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