Immersion Heater Not Heating Water? Here’s Why

An immersion heater not heating water is one of the most annoying problems you can come up with as a homeowner. All you wanted was a nice, toasty shower, and now you’re stuck naked, afraid, and shivering. These bad boys are great for those without access to gas as a heat source, but when they fail it can be a pain to troubleshoot without an electrician. Luckily, there are some things you can check yourself before calling in the big guns.

The most common causes of an immersion heater not heating water are faulty thermostats, damaged immersion elements, limescale buildup, insulation issues, and a tripped breaker.

Let’s break those down a bit, shall we?

Top 5 Causes For an Immersion Heater Not Heating Water

Generally, if your immersion heater stops working, there are some good things to look for. You’ll often find faulty or burnt internal wiring or parts, issues with insulation and wiring, or even just buildup caused by an old heater. Go through the list below to pinpoint the exact cause of your water woes. Alternatively, if you have an electric shower, consider checking out this article to see if it’s the shower that’s causing your problems!

1. Limescale buildup

If you live in an area with notoriously hard water, this is a good place to start. It’s made especially good if you haven’t serviced your water heater in a long time. Limescale buildup occurs when minerals from your water take root in the workings of your pipes and is common in many things that come into contact with water in your home.

Unfortunately, if you’re not confident in your ability to pull apart and reassemble your water heater, it’s likely best that you call a pro for help. Alternatively, you can try a few small things to fix the problem.

  1. Use cleaners – By this, I mean use vinegar. You can flush your water tank and allow a good amount of vinegar to sit in there for a few hours. Flush the tank again and it may have helped.
    1. Do not use heavy chemicals. Seriously, just don’t.
  2. Annually flush your water from the heater. This will flush out any residual minerals that have built up and work as a preventative measure.
  3. Ensure it’s at the proper temperature. You generally want your water to stay below 60°C. Any higher, and calcium and other minerals will be left behind in the tank. It’s best to check your manufacturer’s recommended temperature and follow that to the letter (or in this case, the number).

2. Faulty Thermostat

Some heaters simply have their thermostat fail. It happens, electronics have a lifespan, and sometimes you find that out the hard way. If you have a modern heater with an external thermostat, simply hit the reset button and see if that fixes it. If not, though, do the following:

  1. Cut all power to your heater at the breaker and allow it to cool.
  2. Remove the lid that covers the upper heating element. (Take photos so you can remember where everything went.)
  3. Remove the plastic cap covering the thermostat and avoid touching wiring or electronics.
    1. These are generally really, really sensitive. It’s best to not touch them at all if you can avoid it.
  4. Press the reset button and reassemble everything as it was. Turn the power back on and test it.
  5. If this doesn’t work, call for a pro to replace the thermostat. It’s a rather complicated process best left to those who do this for a living.

3. Damaged or Faulty Immersion Element

This is more common in older machines that are already on the brink of failure, but it’s worth checking nonetheless. If your heater is either a) heating water far too quickly, or b) taking way too long to heat it, it’s likely the immersion element.

The good news is you may have pinpointed the problem! The bad news is that this repair needs electrical and plumbing knowledge. Unless you have that (you wouldn’t be here if you did), it’s time to ask for help. Call a technician for help on this.

4. Insulation Issues

This is another issue it’s best to leave to the pros. If your insulation has broken down in the immersion heater, it’s going to most likely cause damage to wiring, trip your main, and even blow fuses. This is not for the DIY crowd – seriously, call for help on this.

5. Tripped Breaker

If your immersion heater is simply not functioning at all, it’s best to look at your breaker. This may seem obvious, but you’d be surprised how often this is overlooked. To fix this, simply go to your main breaker panel and turn the breaker that’s off, on.

Does the breaker continue to trip repeatedly? That’s a sign that something larger is wrong in your heater or home’s electrical. Do you have a voltage tester? Then you can test this yourself after turning off the power.

If you do decide to test this and don’t turn off the power, you will be electrocuted. Don’t mess with live circuits.

Otherwise, call a pro – but either way, you’ll need a technician to take a look. This is likely not for the DIY crowd to fix, no matter what Mike on that one forum says.

Final Thoughts

If your electric immersion heater is not heating water, you’ll eventually need to call a professional technician. The most common issues with electric immersion heaters are thermostats, insulation, immersion elements, mineral buildup, and issues with the breaker. There are some things you can troubleshoot, such as the thermostat and checking for mineral buildup – but other issues will need a professional to solve.

Water heaters are complicated machines that require electrical and plumbing knowledge to properly repair and troubleshoot. So unless that is something you have an abundance of (again, you wouldn’t be here if that was the case) it’s likely best to make a drink, call a pro, and let them do their thing.

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About the Author Harry Thompson

Involved in home renovations throughout his life, Harry is an expert in everything to do with home and garden DIY. In his spare time, he enjoys cooking and tending to his garden.