How much does it cost to fix boiler error code H.00.42?

Typical repair cost for the boiler H.00.42 fault is £140-£220 including labour.

H.00.42 High

Boiler Fault Code H.00.42

Also written as H0042 — same fault.

Reviewed by the BoilerFaultCodes Editorial Team Last reviewed 7 July 2026

Fault code H.00.42 appears across 1 boiler brand and 7 models. The exact meaning varies by manufacturer — pick your boiler brand below to see the model-specific fix.

Most common meaning Your boiler has stopped working because it cannot correctly detect the water pressure, likely due to a faulty internal sensor or a broken connection. (As reported on Baxi 800)

Pick your boiler brand for the H.00.42 fix

Baxi H.00.42 7 models

Source

Information for the H.00.42 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