Fix an immersion (water tank) heater

⭐ Introduction

An immersion heater, also known as a water tank heater, is an electric heating element fitted inside or attached to a hot water cylinder. It heats the water directly when your main boiler or other heating systems are off or require a boost. Fixing an immersion heater might be needed if your water isn’t heating properly, there’s a leak, or the element has failed.

Common reasons for repair include a faulty heating element, a broken thermostat, or electrical faults. Having a working immersion heater is important for reliable hot water supply, particularly in homes relying on stored hot water.

🔧 What the job involves

Fixing an immersion heater typically involves several tasks:

• Safety checks: Switch off electrical supply at the consumer unit before starting. Verifying the water tank is empty or drained as needed.

• Inspection: Visual and electrical testing of the immersion element, thermostat, wiring, and tank connections.

• Repairs or replacement: Most problems are solved by replacing the faulty immersion element and/or thermostat.

• Electrical work: Carefully disconnecting old components and fitting replacements. Ensuring the new element matches the tank specifications and electrical rating.

• Testing: Turning the supply back on, testing water heating performance, and safe operation of electrical parts.

A qualified heating engineer will also check the system’s wiring condition and ensure compliance with local electrical safety standards (Part P of the Building Regulations applies to fixed electrical installations in dwellings). All work should be carried out using appropriate personal protective equipment and following safe working practices.

📝 Step-by-step from booking to completion

1. Initial enquiry: Contact a Gas Safe or qualified heating engineer to discuss the issue. Even though immersion heaters are electric, a competent heating engineer often handles both gas and electric hot water systems.

2. Survey and quote: The engineer usually visits your home to inspect the immersion heater and assess the problem. They should provide a detailed, written quote before starting any work.

3. Booking a work date: Agree on a convenient date and time for the repair visit.

4. Preparation: Make sure the engineer will have reasonably easy access to the hot water cylinder and electrical consumer unit if needed.

5. Day of work:

   • Engineer arrives and verifies the fault.
   • Switch off electrical supply and drain the tank if necessary.
   • Replace or repair the immersion heater components.
   • Conduct testing and ensure everything works properly.

6. Completion:

   • Restore power and water.
   • Engineer explains the work done and provides any necessary documentation.
   • Keep the paperwork, including any certificates or guarantees.

💷 Main costs to expect

• Labour: £60–£100 per hour, depending on location and engineer’s experience. Repairs typically take 1–3 hours.
• Parts:
  • New immersion element: £40–£80.
  • Thermostat replacement (if needed): £20–£50.
• Extras: Possible cost for draining the hot water cylinder or removing sludge — £30–£80.
• Disposal: Engineer may charge a small fee (£10–£20) to remove old parts.
• Certification: Electrical work under Part P requires certification by the engineer, usually included in the labour cost, but confirm this in advance.

Example: A straightforward element swap with a new thermostat might cost around £150–£250 including labour and parts.

📊 What affects the price

• Accessibility of the hot water cylinder (tight or awkward spaces take longer).
• Complexity of the existing immersion heater system or outdated wiring.
• Need for additional electrical work (e.g., new isolator switch or rewiring).
• Whether the hot water tank requires draining or cleaning before repair.
• Location of property (London and South East generally more expensive).
• Urgency or same-day call-out requests.
• Requirement for certifications or compliance with updated Building Regulations.

⏱ How long does it take?

• Simple replacement: 1–2 hours if parts are readily available and the tank is accessible.
• Moderately complex repair: 2–3 hours if draining cylinder, testing wiring, or replacing multiple components.
• Additional work: Longer if extensive electrical rewiring or tank servicing is needed (could extend to half a day).

🏠 Can you DIY it?

Immersion heaters involve electrical components and potentially hot water systems under pressure, so DIY isn’t recommended unless you have solid electrical and plumbing experience. Safety risks include electric shock and water damage. In the UK, immersion heater installations and repairs within your home must comply with Part P of the Building Regulations, which requires certain work to be inspected and certified by a competent person.

For peace of mind, hire a qualified heating engineer registered with a competent person scheme such as NICEIC or NAPIT. They will provide the necessary test certificates and ensure your system is safe and compliant.

💰 Typical UK price range

Repairs or replacements usually range between £120 and £300 including VAT. Simple element swaps are at the lower end, more involved repairs or replacements with additional parts and work cost more.

Prices do vary by region, trade body, and complexity of the job.

✅ Handy tips before you start

• Prepare access: Clear the hot water cylinder area and ensure safe access to electrical consumer unit.
• Turn off power: Before the engineer arrives, switch off the immersion heater circuit if it’s safe to do so.
• Get written quotes: Always ask for clear, itemised quotes covering labour, parts, and any extras.
• Check engineer registration: Confirm they are qualified and registered for domestic electrical work.
• Aftercare: Keep documents like receipts, guarantees, and Part P certificates for future reference.
• Regular servicing: Consider annual checks to maintain efficiency and prolong appliance life.
• Water quality: Hard water can cause element failures; installing a water softener or descaling system helps reduce problems.
• Emergency prep: Know where your electrical consumer unit switches are to isolate your immersion heater in case of faults.

Having a reliably functioning immersion heater means dependable hot water and peace of mind. When repairs are needed, a qualified heating engineer can efficiently restore your system safely and to regulatory standards.