How much does it cost to fix boiler error code 6C:100?

Typical repair cost for the boiler 6C:100 fault is £180-350 including labour.

6C:100 Medium

Boiler Fault Code 6C:100

Also written as 6C100 — same fault.

Reviewed by the BoilerFaultCodes Editorial Team Last reviewed 27 April 2026

Fault code 6C:100 appears across 1 boiler brand and 5 models. The exact meaning varies by manufacturer — pick your boiler brand below to see the model-specific fix.

Most common meaning Your boiler's internal pump for hot water is stuck running at full speed, which usually means there is a communication error or a part is beginning to fail. (As reported on Viessmann Vitodens 200)

Pick your boiler brand for the 6C:100 fix

Viessmann 6C:100 5 models

Source

Information for the 6C:100 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