BoilerFaultCodesYour boiler has detected an issue with the drainage pump or the flap that prevents fumes from blowing back into the unit, causing it to shut down for safety.
Book a Gas Safe engineer within 24–48 hours. Your boiler may be unsafe or could break down completely if left.
Technical description: Flue gas non-return flap/condensate pump fault
What causes this fault?
This fault occurs when the boiler's internal safety checks detect that either the condensate water cannot be pumped away or the safety flap in the exhaust system is stuck. The most common reason is a mechanical failure or blockage in the pump, which prevents the boiler from safely disposing of waste liquids produced during heating. If the flap is at fault, it is usually because it has become jammed or dislodged, preventing the system from ensuring dangerous fumes are pushed out of the flue correctly.
This fault is more common in winter, as external condensate drainage pipes can freeze, causing water to back up and overwhelm the pump.
Engineer required
This fault requires a Gas Safe registered engineer. Do not attempt gas-related repairs yourself.
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