8H-65 High
The water inside your boiler is heating up too quickly because it cannot flow through your radiators properly.
Technical description: Flow temperature steep rise – the radiator valves may not be open enough to circulate water
Typical repair cost: £0-120 (including labour)
DIY fix possible
Ensure all your radiator valves (TRVs) are turned to the highest settingCheck that any bypass valves or zone valves in your system are openRestart the boiler once you have ensured water can flow through the radiators
Protect yourself from future repair bills
A boiler cover plan would cover faults like 8H-65 — no call-out fees, no surprises.
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Parts commonly replaced
- None (usually a settings issue)
- Circulation pump
- Bypass valve
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