127 Medium
Your boiler has failed to heat the hot water tank to a high enough temperature to kill off bacteria, which is a safety routine it performs periodically.
Technical description: Legionella (cause of Legionnaires’ disease) protection temperature not reached
Typical repair cost: £90-200 (including labour)
DIY fix possible
Check that your hot water cylinder thermostat is not turned down too lowEnsure your hot water timer is set to allow the boiler enough time to complete a full heating cycleReset the boiler to see if the cycle completes successfully on the next attempt
Protect yourself from future repair bills
A boiler cover plan would cover faults like 127 — no call-out fees, no surprises.
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Parts commonly replaced
- Cylinder thermostat
- NTC water temperature sensor
- Motorised zone valve
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