How to Replace an Immersion Heater Element (UK)
Swap a UK immersion element on copper or unvented cylinders: 11" and 14", Backer, Santon, Heatrae Sadia and Megaflo compatibles.
Isolate electrically AND on the mains cold
Switch off at the immersion spur and lock off. Isolate the cold feed. Open a hot tap upstairs to break the vacuum. Drain from the cylinder drain-off point until water stops flowing — do NOT attempt to unscrew a hot immersion head under pressure.
Pick the right length
UK immersion elements come in two standard lengths: 11" (280 mm) for indirect copper cylinders, 14" (355 mm) for direct-heat and combination cylinders. Unvented cylinders (Megaflo, Santon Premier) use Incoloy 825 or titanium elements to resist chlorinated mains water.
- Backer 09763VS — 11" copper element, 3 kW, 2¼" BSP thread.
- Backer 09769VS — 14" copper element, 3 kW.
- Megaflo 95606813 — 11" Incoloy, factory OEM.
- Santon Premier Plus 95606814 — 14" Incoloy, direct-fit.
Refit — thread and seal
Never use PTFE tape on an immersion boss — the seal is a fibre washer that comes with the new element. Wrench-tighten to 45 Nm using an immersion spanner; over-tightening cracks the boss.
Frequently asked questions
- How long does a 3 kW immersion heat 210 L?
- Approximately 90 minutes from 10 °C to 60 °C on a fully insulated cylinder — allow longer on older uninsulated copper.
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