How much does it cost to fix boiler error code 5.viii?

Typical repair cost for the boiler 5.viii fault is £100-250 including labour.

5.viii High

Boiler Fault Code 5.viii

Also written as 5VIII — same fault.

Reviewed by the BoilerFaultCodes Editorial Team Last reviewed 27 April 2026

Fault code 5.viii appears across 1 boiler brand and 3 models. The exact meaning varies by manufacturer — pick your boiler brand below to see the model-specific fix.

Most common meaning Your boiler is struggling to heat water because it is not receiving enough gas to reach the required temperature. (As reported on Chaffoteaux Celtic 24 HE)

Pick your boiler brand for the 5.viii fix

Chaffoteaux 5.viii 3 models

Source

Information for the 5.viii 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 27 April 2026