Emergency
C1 on Worcester Bosch Greenstar Utility 18/25

Your boiler is struggling to breathe because it cannot safely push exhaust gases out through the flue pipe.

Reviewed by the BoilerFaultCodes Editorial Team · Last reviewed

Act immediately

Turn off your boiler and stop using gas appliances. Call a Gas Safe engineer now. This fault can be dangerous if ignored.

Technical description

Flue draught incorrect

Engineer required

This is a emergency severity fault. Stop using the boiler and call a Gas Safe registered engineer. Do not attempt gas-related repairs yourself.

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Related fault codes

C6View →A1View →

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