BoilerFaultCodesYour boiler has stopped working because either its exhaust pipe is obstructed or the pipe that drains away waste water is blocked.
Book a Gas Safe engineer within 24–48 hours. Your boiler may be unsafe or could break down completely if left.
Technical description: Blocked Flue/Condensate
What causes this fault?
This fault occurs when the boiler's internal safety sensors detect that the waste gases or waste liquids cannot exit the unit safely. The most common reasons are a blockage in the plastic pipe that carries water away to a drain, or an obstruction in the large flue pipe on the outside of your property. If these pathways are restricted, the boiler will shut down to prevent hazardous fumes from backing up into the appliance.
This fault is frequently seen during periods of extreme cold when the external condensate pipe can freeze, causing liquid to back up into the boiler.
DIY fix possible
Check the white plastic pipe outside for ice or debris and gently clear itThaw any frozen external pipes using a hot water bottle or warm waterPress the 'Restart' button on the boiler displayEnsure the external flue terminal is not covered by leaves or nests
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A boiler cover plan would cover faults like L0 — 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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