Immersion Heater Replacement London

Standard immersion heater replacement is from £225 fitted in London — that covers the part (a 3kW Incoloy 825 element with thermostat), the drain-down, the fitting, the refill, the electrical safety check and the certificate. Removable-head elements on a Megaflo Eco are cheaper from £185 because no drain-down is needed. Twin-element cylinders fitted with two new elements come in from £345. Out-of-hours calls (evenings, weekends, bank holidays) carry a 20% premium. We always confirm the fixed price on the phone before the engineer is dispatched, and again in writing on site before any work begins. Call 0207 046 1363 for a same-day fixed quote.

Three causes account for ~95% of London immersion failures. First, limescale build-up: London's hard water (especially North and West London) furs the heating element until it overheats and burns out — usually 5–10 years on a copper element, 8–12 years on Incoloy. Second, electrical sheath failure: a pinhole in the element wall lets water reach the live coil, tripping the RCD. Third, thermostat or cut-out failure: the controlling thermostat sticks open or the safety cut-out trips one-shot and locks the element off. A 15-minute resistance and insulation test tells us exactly which fault is present before any work begins.

A standard immersion replacement on a vented or unvented cylinder is a 1.5 to 2 hour job on site. The breakdown is roughly: 10 minutes isolating and testing, 20–40 minutes draining (longer if the drain-cock is seized), 30–45 minutes swapping the element and recommissioning, 15 minutes of electrical testing and certification. A removable-head element swap on a Megaflo Eco is faster — 45 to 60 minutes total, because no drain-down is required. Twin-element jobs take 2 to 2.5 hours. We always confirm the time estimate on the phone.

A full immersion element is one solid unit — the heating coil and the threaded boss are a single screwed assembly. To service it you have to drain the cylinder down to below the element height. A removable head design (used on Heatrae Sadia Megaflo, Santon Premier and some other modern cylinders) splits the element into two parts: a fixed sheath welded into the cylinder, and an internal heating coil that unscrews from the head. You swap just the coil — no drain-down, no disturbance to the cylinder. Faster, cheaper, and less risk on a 20-year-old cylinder where you don't want to disturb scale.

Yes — and it's an increasingly common request after combi breakdowns leave families without hot water. The two routes are: a small unvented mini-cylinder (30–50L) with its own immersion, plumbed in at the kitchen or main bathroom; or a fully electric instantaneous water heater that bypasses the combi entirely. We recommend the mini-cylinder route for most London families because it gives 20–30 minutes of hot water at full flow during a combi outage. Install cost is from £395 fitted on a single sink, from £595 fitted on a bathroom. Worth doing for any household with elderly or young children. Call 0207 046 1363 for a survey.

The immersion element itself is a plumbing job — replacing the element does not on its own require an electrician. However, where the immersion circuit is being newly installed, modified (cable upgraded, isolator changed) or where the work is in a 'special location' under Part P of the Building Regulations, the electrical part must be certified by a registered electrician. Our G3 engineers are also Part-P registered, so we cover both sides in one visit. The Building Regulations Part P notification is filed within 30 days of any notifiable work, and you get the EICR-style minor works certificate by email.

Most modern UK cylinders take an 11-inch (280mm) element. Older Range Tribune, older Gledhill EnviroFoam and a handful of pre-2000 vented cylinders take a 14-inch (355mm) element. The boss diameter on every UK cylinder is BSP 2¼ inch. Photo of the existing element with a tape measure across it confirms the length in 10 seconds. On a twin-element cylinder the top element is shorter (heats the upper third for daily use) and the bottom element is longer (heats the full tank on a boost). We carry both 11 and 14 inch elements on the van.

Only if the work is not G3 certified. Approved Document G3 makes any service or modification to an unvented hot water vessel a controlled activity that must be carried out by a G3 qualified engineer. If your element is replaced by a non-G3 plumber, your cylinder warranty (typically 25 years on the tank, 2 years on parts) is void. Every ERL engineer holds a current G3 ticket (BPEC or LCL Awards). We log the work in the Benchmark logbook and the warranty stays in place. On vented cylinders G3 does not apply — but we still keep the same paperwork standard.

An RCD-tripping immersion almost always means the element's metal sheath has failed and is allowing leakage current to earth. The fault grows progressively: at first the RCD only trips at the end of a long heat cycle, then it trips on every heat-up, finally it trips the moment the immersion is switched on. The fix is a new element — the existing one is not safe to keep using. We test with an insulation resistance meter (must read above 1 megohm at 500V DC); anything below tells us replacement is the only safe option. Do not be tempted to bypass the RCD or run the immersion on an isolated circuit.

Yes, with one caveat. Solar PV diverters (Solic 200, MyEnergi Eddi, Marlec Solar IBoost+) modulate the power going to the immersion across the day. A standard 3kW element handles this fine. For maximum life on PV setups we recommend a low-watt-density element (1.5kW or 2kW spread over the same physical length) — the lower power density runs cooler and resists scale far better when the immersion is being heat-cycled 6–8 times a day on intermittent sunshine. Install cost is the same; the element itself is a £15–25 premium. Worth specifying when the existing PV diverter is going onto a 10-year-old cylinder.

Every immersion element on an unvented cylinder must include a non-self-resetting energy cut-out — a one-shot thermal fuse that trips at 85°C and physically isolates the element. This is the third layer of safety after the thermostat and the T&P valve, mandated by Approved Document G3 and BS EN 12897. Once tripped, the cut-out cannot be reset by the homeowner — it must be replaced (it's usually integrated with the thermostat). A tripped cut-out always has a cause: a failed thermostat, a stuck motorised valve on an indirect cylinder, or low water level in the cylinder. We diagnose the cause before fitting the new element, otherwise the new cut-out trips again.

On an unvented cylinder, the annual G3 service includes a resistance and insulation test on every immersion element fitted — that's the requirement. On a vented cylinder there's no statutory annual test but we recommend the same yearly check, especially on hard-water London postcodes. The test takes 60 seconds with a multimeter and an insulation tester. Early warning signs (resistance creeping up, insulation resistance creeping down) let us plan a £225 element replacement at a convenient time, rather than waiting for a Sunday-night failure. Bookable as a £155 standalone visit or bundled with a £155 cylinder G3 service.

We fit Backer (the UK standard, made by NIBE in Lincolnshire), Heatrae Sadia (the OE on Megaflo cylinders), Santon, Tesla, and Range OE elements. All of our standard fits are Incoloy 825 sheath, 3kW, with integrated thermostat and non-self-resetting energy cut-out. Where the cylinder manufacturer specifies a proprietary part (e.g. a Megaflo Eco coil) we fit OE only — using a generic part voids the cylinder warranty. We do not fit cheap Far-East copper-sheath elements; the failure rate on London water hardness makes them a false economy by year four.

Yes. The element itself carries a 12-month manufacturer warranty (Backer, Heatrae Sadia and Santon all match this — some go to 24 months on registered installs). Our workmanship is guaranteed for 12 months: if the joint leaks, the thermostat fails to set point, or the electrical install fails an EICR within a year, we return at no cost. The Benchmark logbook entry and Building Control notification (where applicable) are filed within 30 days. All paperwork is emailed the same day. Call 0207 046 1363 or WhatsApp 07456 975436 to book.

Yes, in roughly 80% of London calls. We carry the four most-fitted elements (Backer 3kW Incoloy 11" and 14", Heatrae Sadia Megaflo head, Santon Premier head) on every van. Same-day replacement depends on the cylinder being identifiable from a phone photo of the data plate, the boss not being seized solid (older Gledhill and Range cylinders can take 30 minutes of penetrating oil), and an electrical isolator being accessible. We confirm same-day availability on the phone within 5 minutes. Out-of-hours and weekend cover is available with a 20% premium on the labour rate.