How much does it cost to fix boiler error code 1200 mm?

Typical repair cost for the boiler 1200 mm fault is £250-500 including labour.

1200 mm Emergency

Boiler Fault Code 1200 mm

Also written as 1200MM — same fault.

Reviewed by the BoilerFaultCodes Editorial Team Last reviewed 7 July 2026

Fault code 1200 mm appears across 1 boiler brand and 1 models. The exact meaning varies by manufacturer — pick your boiler brand below to see the model-specific fix.

Most common meaning Your boiler is warning that the outside flue pipe is dangerously close to an opening like a window or door, which could lead to exhaust fumes entering your home. (As reported on Malvern TenTwenty)

Pick your boiler brand for the 1200 mm fix

Malvern 1200 mm 1 model

Source

Information for the 1200 mm fault code is sourced from the official service / installation manual for each model that displays it. Read more about how we source fault codes →

Reviewed by the BoilerFaultCodes Editorial Team · Last reviewed 7 July 2026