Need help? Hire the professionals

Get a free quote from the London Property Service specialists here at My Plumber

Get a free quote right now

View Our Simple Price List
Generic selectors
Exact matches only
Search in title
Search in content
Post Type Selectors

Immersion Heater Not Working – Find Out Why and What to Do

An expert repairing a faulty immersion heater

It’s that time again. You are thrilled, expecting that hot shower you’ve been planning all day. Pressing the hot shower tap, you hope to get that steady stream of warmed water and enjoy that tiny moment of total relaxation. It’s such a downer when the following blast of cold water ruins all your expectations. 

Well, you’re probably wondering why the immersion heater is not working. The straight answer is that the culprit may be anything from a faulty thermostat to damaged elements, and even limescale buildup. So, read along to find out why there is no hot water in your immersion heater and how you can resolve that problem.

What is an Immersion Heater

Both cylinder immersion heaters and hot water heaters use a well-protected steel tank. The most common trait linking the two appliances is that there’s strong insulation between the storage unit and the steel coat. It’s there to diminish heat loss. 

The main distinction is that immersion heaters use electricity as a warmth source, so there is a heating element inside the cylinder. In comparison, gas water heaters use a gas burner located beneath the tank unit. Many homeowners prefer to use the latter because heating your water with electricity is more costly than doing so with gas.

How Does an Immersion Heater Work

A steady flow of electricity goes through the heating element, which, in response, heats the water right inside your tank. Also, an internal or external thermostat regulates the temperature of your water, keeping it ready for use for your peace of mind. 

So, whenever you turn on a tap, a cold, high-pressure stream of fresh water enters the tank and pushes the heated water out. Once the temperature is high enough, the water rises to the top of your cylinder, right next to the heating element.

As for the wiring part, immersion heaters are usually connected to your central electrical supply. But don’t worry in case of a power outage; it preserves the heated water until you deplete it. 

The best part is that you can turn the immersion heater on and off, as there’s no reason to warm the water in the cylinder continuously.

Common Immersion Heater Problems and Solutions

Now that you know how the unit works, it’s time to look at the most common issues. By the end of this article, you will know what it takes to make a full immersion heater fault diagnosis.

The circuit breaker has tripped

A cylinder that doesn’t seem operational and provides no warm water can be out of electrical power. Often, when the circuit in the breaker box overloads, it trips down to avoid overheating. Be glad about it, though, because that means you won’t be dealing with an electrical house fire.


To start, see if the immersion heater’s circuit breaker is on. You can find it in the main breaker panel. On the off chance that the breaker has tripped, switch it off, then switch it back on once more. Then wait and see if the switch trips again. If it does, you might be dealing with a more significant issue.

Caution: Immersion heaters work with 220 to 240 volts of electricity. Remember, it’s incredibly hazardous to diagnose any internal parts of the heater while the power is still on. For your safety, switch the circuit breaker off and use a voltage tester to check if any electrical current goes through the heater’s wires.

You have a faulty thermostat

Sometimes, immersion heaters stop unexpectedly, or the water that comes out is singing hot. The odds are that the thermostat is faulty. With some luck, you might fix the issue with a simple reset of the regulator, so let’s see how this is done.


If you have a more modern system with an external thermostat, simply press the reset button on it. For older heaters, follow the instructions:

  • Cut the power to your immersion heater by switching the circuit breaker off.
  • Remove the lid that protects the upper heating element of your unit.
  • Carefully remove the plastic safety cap and try not to touch any wires and other electrical fixtures.
  • Press the small button that has “Reset” written next to it. Depending on the model of your heater, you may need a small pin to reach the switch.
  • Assemble everything back and make sure that the safety cover is well-placed. 
  • Turn the power on and test the immersion heater.

And if that doesn’t work, call a specialist to replace the burned thermostat, since the task may seem daunting for someone with little to no experience. So, save yourself the hassle and book a professional heating specialist to help you out with immersion heater repairs!

A damaged immersion element

Such problems usually occur towards the end of the immersion heater’s lifespan. That happens because of the rust that damages the component circuit, and while the unit keeps on working for a reasonable time, there are some definite signs that something’s wrong with it. 

For example, it can take forever for your immersion heater to warm the water or the opposite – the unit can heat it faster than expected. Also, as a result of the damage to the element, the heater can switch on and off unexpectedly.


Unfortunately, fixing the immersion heater’s central component is a challenging task, and even the bravest of DIY experts will have a tough time with it. Overall, the process includes removing the old heating element, cleaning the heater’s opening and fitting the new component. 

However, it’s easier said than done as the task requires some prior experience in plumbing and a bit of knowledge about electrical fixtures. So, for your safety, please contact a professional technician to change the element and ensure that everything works fine.

Limescale buildup

If you live in an area with more hard water, limescale builds up in excess, and your immersion heater breaks faster than expected. Additionally, significant issues arise when the compound builds around your heating element, creating a bottleneck in your entire system. With a domestic water softener installation you won’t struggle with limescale issues and will save on maintenance costs. 


You might be able to avoid limescale build-up by asking a specialist to fit a filter that prevents such compounds from entering in the first place. In addition, you could take the immersion heater down and flush out the scale with a high-pressure water stream. 

We recommend that you avoid disassembling your immersion heater if you lack the required expertise to do so!

Problems with the insulation

When your immersion heater experiences an insulation breakdown, it typically disrupts the electrical current flow through the heating element. As a result, the overloaded system can damage wires, blow fuses, and even cause tripping of your main circuit breaker.


A heating expert can investigate your immersion heater’s element and wiring, and determine if any parts need servicing or replacement. We do not endorse DIY repairs of the internal problems with your immersion heater, as it can be dangerous for your health.


Immersion heaters are a well-known alternative if you lack a gas supply. They can serve you right for a very long time; nevertheless, issues may arise, and when that happens, it’s usually because of:

  • Burned or faulty internal parts, such as a heating element or a temperature regulator;
  • Problems with the wiring or the electrical insulations;
  • Limescale buildup or issues that come up with older immersion heaters;

Immersion Heater Not Working – Find Out Why and What to Do

Need help? Hire the London Property Service experts today by giving us a call on 020 3078 5920.

Award Winning Property Services in London

We very proud that over the past decade our amazing team of skilled Plumbers, Gas Engineers, Electricians, and Handymen have been recognised by winning awards and being finalists for multiple awards across London

Hounslow Business Awards 2016
Hounslow Business Awards 2015
London Business Awards 2014
Hounslow Business Awards 2013
24 hour emergency helpline
020 3078 5920
Your call may be recorded for training or quality purposes
Calls may be answered via a call centre during out-of-hours