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Posted: 2nd December 2025 | Author: Adam Brown
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Immersion heaters are a popular way to heat water. They are reliable, easy to use and work well as either a backup or your main hot water source. But when yours suddenly stops working, it can be a real hassle, especially if you rely on it for everyday use.
Here, we break down the most common reasons immersion heaters stop working. Let’s figure out whether you have an easy fix or if it might be time for a replacement.
If your immersion heater has stopped working, finding the issue quickly will save you a real headache. You might even avoid a costly repair! We find that most problems are quite simple to resolve on your own. Here are some of the most common issues to look out for:
If your immersion heater has stopped working all of a sudden, a very common reason is a tripped circuit breaker. This often happens if there is a fault in the heater or an overloaded circuit.
Find your consumer unit (fuse box or fuse board) and check whether the immersion switch has tripped. If so, simply reset it and see if the heater starts working. If it trips again quickly after, this could mean there is a more complex issue and it needs to be checked by a qualified electrician.
If your immersion heater isn’t heating water or is overheating, the thermostat is likely to be to blame. Over time, thermostats can fail. This prevents the heating element from receiving the correct signals.
Replacing a thermostat can be straightforward and relatively low-cost, especially if you're already comfortable working with electrics. See a qualified electrician for advice.
The heating element inside the cylinder is basically the heart of your immersion heater. If it burns out or becomes damaged, your system is not going to heat water effectively. Signs of a faulty element include cold water running even when the system is switched on, or the circuit tripping as soon as it’s engaged.
You can often diagnose a failed element using a multimeter to test continuity. If there’s no continuity, the element needs to be replaced.
Do you live in a hard water area? You might have a limescale buildup on your immersion heater element. Limescale acts in the same way as insulation, making it harder for the element to heat water efficiently. This can lead to overheating or complete failure.
Hard water can damage plumbing systems over time. Consider using a water softener to help prolong the life of your heater and other appliances.
Insulation on the hot water cylinder is crucial for retaining heat. If this insulation is damaged or degraded, your water may cool too quickly or the heater may have to work harder than needed. This can lead to failure.
Check the cylinder jacket or foam insulation for signs of wear, dampness or gaps. Replacing or upgrading the insulation can improve performance and efficiency.
A high-quality immersion heater can last anywhere between five and ten years. Ultimately this depends on how often it is used, how well it is maintained and the quality of the water in the area. In areas with hard water, heaters will likely have a shorter lifespan due to limescale buildup on the element.
Regular maintenance can help to extend the life of your heater. This includes flushing out the tank if it can be accessed, checking the thermostat and replacing sacrificial anodes if needed.
Tough question, but If your heater is near the end of its lifespan or regularly experiencing problems, it is often more cost-effective to replace it altogether rather than continue paying for repairs. The decision usually comes down to the age of your system, how severe the problem is and how often issues keep cropping up.
Common fixes, such as replacing a thermostat or resetting a circuit breaker, are often low-cost and easy to do yourself. However, if small problems keep returning the costs can quickly add up.
You should think about replacing your immersion heater if it is over eight to ten years old, has a damaged part or suffers from heavy limescale buildup. Newer models are often more energy efficient and heat water quicker. This can help lower your energy bills and save you time in the long run.
At Nationwide Supplies, we offer a huge range of immersion heaters, including models specifically designed for use with copper and stainless steel cylinders.
If you're upgrading or replacing a broken unit, contact our expert team; we’re always happy to help.
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The Author: Adam Brown
With a background as a Mechanical Engineer, I started Nationwide Supplies alongside my brother with a vision to modernise what seemed a stuck-in-its-ways industry in the builders merchant sector. Since 2011 it has been my goal to source quality products at the correct prices to be able to offer a saving to customers along with high quality customer service which offers quick delivery and superior technical knowledge in the industry.
