BoilerFaultCodesYour boiler is unable to get rid of waste gases or waste water safely, which has caused it to shut down for protection.
Book a Gas Safe engineer within 24–48 hours. Your boiler may be unsafe or could break down completely if left.
Technical description: 1 Check if condensate pipe blocked/frozen 2 Check if flue blocked 3 If fault persists, contact installer
What causes this fault?
This fault occurs when the boiler's sensors detect a blockage that prevents the safe removal of exhaust gases or waste water. The most common reason is a buildup of debris in the condensate trap or a physical obstruction in the external flue pipe. If these paths are blocked, the boiler automatically shuts down to prevent dangerous fumes from entering your home or water from backing up into the internal components.
This fault is significantly more common during freezing winter temperatures, as the external condensate pipe can freeze and prevent waste water from draining away.
DIY fix possible
Check the white plastic pipe outside for ice and pour warm water over it if frozenEnsure the external flue terminal is not obstructed by leaves, nests, or debrisCheck that the internal condensate trap isn't visibly full of sludge
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A boiler cover plan would cover faults like Blocked Flue/Condensate — no call-out fees, no surprises.
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Could it be time for a new boiler?
If repair costs are adding up, a new energy-efficient boiler could be the smarter long-term choice.
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