How much does it cost to fix boiler error code GTH90?

Typical repair cost for the boiler GTH90 fault is £150-300 including labour.

GTH90 Emergency

Boiler Fault Code GTH90

Reviewed by the BoilerFaultCodes Editorial Team Last reviewed 7 July 2026

Fault code GTH90 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 has detected that exhaust gases are not escaping properly, likely because the flue outside is obstructed or damaged. (As reported on Grant Vortex)

Pick your boiler brand for the GTH90 fix

Grant GTH90 1 model

Source

Information for the GTH90 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