E18 High
Your boiler has shut down because the internal water has become too hot, usually because it isn't moving through the pipes properly.
Technical description: Flow overheat – check water circulation
Typical repair cost: £150-£450 (including labour)
DIY fix possible
Check that your home's radiator valves are fully open.Ensure the boiler pressure gauge is between 1 and 1.5 bar.Try resetting the boiler to see if the fault clears.
Protect yourself from future repair bills
A boiler cover plan would cover faults like E18 — no call-out fees, no surprises.
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Parts commonly replaced
- Circulation pump
- Heat exchanger (flushing debris)
- NTC thermistor
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