F.77 High
Your boiler has detected an issue with the drainage system that removes leftover liquid from the exhaust pipe or a fault with the safety flap inside the flue.
Technical description: Flue non return flap condensate pump error
Typical repair cost: £120-280 (including labour)
Engineer required
This fault requires a Gas Safe registered engineer. Do not attempt gas-related repairs yourself.
Protect yourself from future repair bills
A boiler cover plan would cover faults like F.77 — no call-out fees, no surprises.
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Parts commonly replaced
- Condensate pump
- Flue non-return flap
- Wiring harness
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