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If your immersion heater has stopped producing hot water, is taking longer than usual to heat up, or keeps tripping your electrics, a faulty immersion heater could be the cause. Replacing an immersion heater is often a cost-effective way to restore your hot water supply without needing to replace the entire unit. However, because the process involves both electricity and water, it’s important to follow the correct safety procedures and ensure the replacement is carried out properly. In this guide, we’ll explain the most common signs of immersion heater element failure, what checks to make before replacing it, the tools you’ll need, and the steps involved in safely installing a new element. Yes, immersion heater elements can be replaced if the power and water supplies are safely isolated and the correct tools are used. However, because the job involves both electrical and plumbing work, most homeowners tend to get a qualified electrician or plumber to do the job. If installed correctly, replacing a faulty immersion heater can restore hot water quickly and cost significantly less than replacing the entire immersion heater or cylinder. An immersion heater is an electric heating element installed inside a hot water cylinder or storage tank. It heats water directly by converting electricity into heat, providing a reliable source of hot water for domestic, commercial, and industrial buildings. Immersion heaters are usually used as a primary heat source or as a backup to a boiler or central heating system. They contain a metal heating element, typically made from copper, brass, Incoloy, stainless steel, or titanium, which is submerged in water and transfers heat directly into the cylinder. Because immersion heaters operate independently from the boiler, they can provide hot water even when the central heating system is switched off. An immersion heater works by passing electricity through a metal heating element that is submerged in water. As the element heats up, thermal energy is transferred directly into the surrounding water until the desired temperature is reached. A thermostat monitors the water temperature and switches the heater off when the set temperature has been achieved. Immersion heater elements can fail for several reasons, from age and limescale build-up to electrical faults and overheating. Identifying the underlying causes can help to prevent repeat failures, improve efficiency, and extend the lifespan of your hot water system. Below are some of the most common reasons an immersion heater element stops working. Over time, heat, moisture, and general wear can damage the internal wiring inside the immersion heater element. If the wiring breaks down or shorts against the casing, it may cause blown fuses, tripped circuit breakers, or a complete loss of hot water. Repeated electric tripping is the most common sign of a failed immersion heater element. In hard water areas, minerals naturally build up on the surface of the heating element over time. As limescale builds up, it acts as an insulating barrier, forcing the element to work harder and operate at higher temperatures. This reduces energy efficiency, increases energy consumption, and can significantly reduce the lifespan of the element. Pro Tip: Incoloy and titanium heater elements are often recommended for harder water areas due to their improved resistance to limescale-related wear. Like any heating component, immersion heater elements have a limited lifespan. Constant heating and cooling cycles gradually weaken the internal components and protective casing, eventually leading to reduced performance or complete failure. Most immersion heater elements last between 3 and 5 years, although lifespan can vary depending on water quality, usage levels, and maintenance. Running an immersion heater at unnecessarily high temperatures for long periods of time can place additional strain on the element and encourage faster limescale formation. Over time, this can accelerate wear and increase the likelihood of failure. For most domestic systems, maintaining a moderate temperature of around 60°C provides an effective balance between efficiency, safety, and performance without unnecessary wear. Certain water conditions can gradually corrode the metal sheath surrounding the heating element. As corrosion progresses, cracks or holes may develop, potentially allowing water to reach live electric components. In more severe cases, corrosion can lead to electrical faults, leaks, and complete element failure. A faulty or incorrectly installed thermostat can prevent an immersion heater from regulating water temperature correctly. This may cause the heater to run continuously, overheat, activate the safety cut-out, or produce excessively hot water. If your immersion heater frequently shuts itself off unexpectedly or the water temperature becomes unusually high, the thermostat may need replacing rather than the element itself. Dry firing occurs when an immersion heater is switched on before the heating element is fully submerged in the water. Without water to absorb the heat being generated, the element can overheat within minutes and suffer permanent damage. This commonly happens after draining a hot water cylinder for maintenance or repairs. Pro Tip: Never restore power to an immersion heater until the cylinder has been completely refilled with water. Common signs of immersion heater element failure include: If you notice one or more of these symptoms, the immersion heater element should be inspected before further damage occurs. Before replacing an immersion heater element, it’s important to confirm that the element itself is causing the problem. In some cases, the issue may be related to the thermostat, wiring, fuse, or power supply rather than the element itself. Because an immersion heater involves electricity and hot water, always isolate the power supply before carrying out any inspection. If you’re unsure at any stage, stop what you’re doing and contact a qualified electrician or plumber. Before assuming the immersion heater element has failed, inspect the fuse, isolator switch, and circuit breaker supplying power to the heater. A blown fuse or tripped breaker may indicate a temporary electrical fault rather than a failed element. However, if the circuit continues to trip whenever the immersion heater is switched on, this can often indicate an internal fault within the heating element. A resistance or insulation test can help determine whether the immersion heater has failed internally. These tests are usually carried out using a multimeter or specialist electrical testing equipment. Common faults include broken internal wiring, insulation breakdown, and short circuits that may not be visible from the outside. Pro Tip: Repeated circuit breaker trips are one of the most common signs of a faulty immersion heater element. A faulty thermostat can produce many of the same symptoms as a failed immersion heater element, including no hot water, inconsistent temperatures, and overheating. Before replacing the element, inspect the thermostat and test that it’s operating properly. In some cases, replacing the thermostat may solve the problem without the need for a new element. If you live in a hard water area, inspect the immersion heater for visible signs of limescale build-up. Thick deposits can reduce heating efficiency, increase operating temperatures, and place additional strain on the element. If the element is heavily coated, replacing the element is often more practical and cost-effective than attempting to clean it. Inspect the area around the immersion heater element for signs of corrosion, staining, or leaks. Visible deterioration can indicate that the element has reached the end of its service life. Addressing corrosion early on can help prevent potential damage to the hot water cylinder and surrounding components. Selecting the right immersion heater element material can help improve performance, reduce maintenance, and extend the overall lifespan of your hot water system. Choosing a material that suits your local water conditions can improve efficiency, extend lifespan, and reduce the risk of element failure. Before starting any work, make sure you have the correct tools and safety equipment available. Having everything prepared in advance will help make the replacement process safer, quicker, and more efficient. While replacing an immersion heater element is relatively straightforward for experienced DIYers and qualified tradespeople, using the correct tools can help prevent damage to the cylinder, pipework, and electrical components. Having the correct equipment ready before you begin can help prevent unnecessary delays and reduce the risk of causing further damage during removal and installation. Pro Tip: A dedicated immersion heater spanner provides significantly better grip and leverage than standard hand tools. This reduces the risk of damaging the immersion heater boss or hot water cylinder when removing a tight or heavily scaled element. Replacing an immersion heater element requires careful preparation and attention to safety. Because you’ll be working with both electric and plumbing systems, it’s essential to isolate the power supply, drain the cylinder correctly, and ensure the new element is installed securely. Follow the steps below to replace an immersion heater element safely. Switch off the electricity supplying the immersion heater at the main and isolate the water supply to the cylinder. Before touching any wiring, use a multimeter to confirm that the circuit is completely de-energised. Never rely solely on a switched-off immersion heater control or timer. Attach a hose to the drain valve at the base of the cylinder or position a suitable container beneath the drain point. Open a nearby hot water tap to allow air into the system and help the cylinder drain more efficiently. Continue draining until the water level falls below the immersion heater element. Carefully unscrew and remove the immersion heater cover to expose the thermostat and wiring connections. Before disconnecting any wires, take a photograph of the existing wire arrangement so reconnection is much easier later on. Loosen the terminal screws and carefully disconnect the wiring from the immersion heater. Ensure that the wires are positioned safely away from the work area before proceeding with the removal. Using an immersion heater spanner or box spanner, carefully loosen the existing element and remove it from the cylinder. Older elements can tend to be more difficult to remove due to corrosion, limescale, or prolonged exposure to heat. Apply steady pressure and avoid excessive force that could damage the cylinder fitting or surrounding pipework. Inspect the cylinder threads for debris or damage, and clean the area if needed. Wrap PTFE tape around the threads of the replacement immersion heater element before carefully screwing it into position. Tighten the element securely in place, but avoid overtightening, as this may damage the threads or compromise the seal. Reconnect the electrical wiring exactly as it was before removal, using your photo as a reference if needed. Check that all terminal connections are secure and that no wires are trapped or under tension after replacing the cover. Close the drain valve and restore the water supply to the cylinder. Leave a hot water tap open until the water flows consistently, allowing trapped air to escape from the system. Also make sure to check around the newly installed element for any signs of leakage. Once the cylinder is full of water, restore power to the immersion heater and allow it to operate normally. Check carefully for leaks, unusual noises, and correct water heating performance. If the circuit trips or the heater fails to work properly, isolate the power and investigate the fault before continuing. Important: Never switch on an immersion heater before the cylinder is refilled with water. Doing so can result in dry firing, which can cause permanent damage to the new heating element within minutes. Replacing an immersion heater element is usually much more affordable than replacing the entire unit. The overall cost will depend on the type of replacement element, your location, and whether you carry the work out yourself or hire a professional. In most cases, homeowners can expect to pay between £70 and £120+ for a professionally installed replacement. Costs can vary depending on the element type, cylinder accessibility, and regional labour rates. Replacing a faulty immersion heater element is often one of the most cost-effective ways to restore your hot water supply without replacing the entire unit. By identifying the signs of failure early, carrying out the appropriate safety checks, and choosing the right replacement material for your water conditions, you can improve the efficiency, reliability, and lifespan of your hot water system. Whether you’re dealing with limescale build-up, electrical faults, corrosion, or general wear and tear, selecting a high-quality replacement element can help to provide consistent performance and reduce the risk of future issues. If you’re unsure which immersion heater is right for your system, our expert team is on hand to help. We can advise on the best option for your application, whether you’re replacing a failed element, upgrading your unit, or sourcing a more durable long-term solution. Explore our range of immersion heater elements online, including brass, Incoloy, and stainless steel options, designed to deliver reliable performance and built to last.Can You Replace an Immersion Heater Element Yourself?
What is an Immersion Heater?
How Does an Immersion Heater Work?
Common Causes of Immersion Heater Element Failure
Electric Faults
Limescale Build-up
Age and General Wear
Excessive Heat and Overuse
Corrosion
Faulty Thermostat
Dry Firing
Signs Your Immersion Heater May Have Failed
What to Check Before Replacing an Immersion Heater Element
1. Check the Fuse or Circuit Breaker
2. Test the Element for Electrical Failure
3. Check the Thermostat
4. Inspect for Limescale Build-up
5. Check for Visible Corrosion or Leaks
Choosing the Correct Replacement Material
Material Best Suited For Key Benefits Copper Soft water areas Cost-effective Brass General domestic use Good durability and corrosion resistance Incoloy Medium to hard water areas Improved limescale build-up resistance Titanium Very hard or aggressive water conditions Good corrosion and limescale resistance Tools Needed to Replace an Immersion Heater Element
Tool Purpose Immersion heater spanner or box spanner Removes and installs the immersion heater elements Adjustable wrench Tightens and loosens fittings Screwdriver Removes electrical covers and terminals Pipe wrench or grips Provides additional leverage for seized elements PTFE tape Creates a watertight seal Replacement immersion heater element Replaces the faulty one Hose or bucket Drains water from the hot water cylinder Multimeter Confirms power isolation and tests electrical continuity Safety gloves and protective goggles Protects against sharp edges, hot water, and debris How to Replace an Immersion Heater Element
1. Turn Off the Power and Water Supply
2. Drain the Hot Water Cylinder
3. Remove the Electrical Cover
4. Disconnect the Wiring
5. Remove the Old Immersion Heater Element
6. Install the New Element
7. Reconnect the Wiring
8. Refill the Cylinder
9. Test the Immersion Heater
How Much is it to Replace an Immersion Heater Element?
Typical Immersion Heater Element Replacement Costs
Item Average Cost Replacement immersion heater element £20 – £45 Thermostat (if needed) £10 – £30 Electrician/plumber costs £50 – £75+ Total installation cost £70 – £120+ Replacing Immersion Heater Elements – Final Thoughts
