Immersion Heater Repair & Replacement
Professional immersion heater repair and replacement by qualified electricians. Faulty elements, thermostats, timer switches, and cylinder wiring. Qualified and insured.
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Immersion Heater Repair & Replacement
Qualified electrician
Same-day service
Most jobs matched within hours.
Upfront pricing
Clear quotes before work starts.
Qualified pros
NICEIC & NAPIT registered.
Pay when done
Funds held until you're happy.
How it works
Symptom assessment and isolation
The electrician discusses the symptoms — no hot water, lukewarm water, tripping electrics, or timer not working. The immersion circuit is isolated at the consumer unit and the double-pole switch. The thermostat cover is removed from the top of the cylinder to access the wiring and controls.
Electrical testing
The electrician tests the immersion element for continuity (to check if it has failed open-circuit) and insulation resistance (to check for earth faults that cause tripping). The thermostat is tested for correct operation — checking that it switches the element on and off at the correct temperatures. The timer switch and wiring are tested for continuity and correct connection.
Component replacement
The faulty component is replaced. If the element has failed, the cylinder is drained (or a freeze kit is used), the old element is removed with an immersion spanner, and a new element is fitted with a new fibre washer. If the thermostat has failed, it is replaced and set to the correct temperature (typically 60°C). Timer switches are replaced at the wall position.
Refilling and testing
If the cylinder was drained, it is refilled and checked for leaks around the element seal. The circuit is re-energised and the immersion is tested for correct heating. The thermostat is verified to cut out at the set temperature. The timer switch cycle is confirmed. The circuit is re-tested for insulation resistance to confirm no faults.
What's included
What's involved
Immersion heater repair and replacement covers diagnosing and fixing faults with the electric heating element, thermostat, timer switch, and wiring of a hot water cylinder's immersion heater. Common problems include no hot water (failed element or thermostat), water too hot or not hot enough (thermostat fault), tripping electrics (element insulation breakdown), and timer not working (faulty timer switch or wiring). The electrician tests the immersion circuit, identifies the faulty component, and replaces it — restoring reliable hot water.
Immersion heaters operate at mains voltage (240V) and are typically on a dedicated 16A or 20A circuit with a double-pole isolator switch. The heating element is submerged in water inside the cylinder, making the combination of electricity and water particularly hazardous. A failing element can develop an earth fault that trips the RCD or, worse, makes the cylinder pipework live. Replacing an immersion element involves draining the cylinder, using a specialist element spanner, and making high-current electrical connections — work that requires both plumbing and electrical competence.
Get a personalised quote
Typical cost: £100–£300per repair
Every job is different — pricing depends on your property, location, and specific requirements. Describe what you need and a qualified electrician will quote you directly.
How long does it take?
1-3 hours depending on the fault. Thermostat or timer replacement takes about an hour. Element replacement takes 2-3 hours including draining, fitting, and refilling the cylinder.
Regulations & safety
Safety notice
Always isolate the immersion heater at the double-pole switch and the consumer unit before any work. The element terminals inside the cylinder cover carry mains voltage and are in close proximity to water and metal pipework — contact is potentially fatal.
Never reduce the thermostat below 60°C to save energy. Water stored below 60°C can harbour Legionella bacteria, which causes Legionnaires' disease — a serious and sometimes fatal form of pneumonia.
If the immersion heater is repeatedly tripping the RCD or MCB, do not keep resetting it. A tripping element has an insulation fault that is leaking current to earth through the water. Continued use risks electric shock via the pipework and taps.
BS 7671:2018+A2:2022 (IET Wiring Regulations)
Immersion heater circuits must comply with BS 7671. The circuit requires a dedicated radial circuit with appropriate MCB/RCBO protection and a double-pole isolator switch adjacent to the cylinder. The wiring must be heat-resistant (typically 3-core flex rated for the element temperature) from the isolator to the element terminals.
Part P of the Building Regulations (Approved Document P)
Replacing an immersion element or thermostat on an existing circuit is generally non-notifiable maintenance work. However, if a new circuit needs to be run from the consumer unit (e.g., replacing an old radial circuit), this is notifiable under Part P.
HSE — Legionella and Water Temperature
Hot water must be stored at a minimum of 60°C to prevent Legionella bacteria growth, as recommended by the HSE Approved Code of Practice L8. The thermostat should be set to 60°C — not lower for energy saving, as this creates a health risk.
What to expect
Having issues with your existing installation?
Already have a immersion heater repair & replacement and having issues? Check our troubleshooting guides.
RCD Keeps Tripping? Common Causes & How to Fix It (2026)
Your RCD keeps tripping and cutting power to multiple circuits. This guide covers every common cause — from faulty appliances and moisture to wiring faults and nuisance tripping — plus exactly what to do about it.
No Power In The Whole House
Your entire home has lost electricity. No lights, no sockets — everything is dead.
Frequently asked questions
How do I know if my immersion heater has failed?
Why does my immersion heater keep tripping the electrics?
Can I replace an immersion heater element myself?
What temperature should the thermostat be set to?
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