How much does it cost to fix boiler error code E785?

Typical repair cost for the boiler E785 fault is £150-250 including labour.

E785 High

Boiler Fault Code E785

Reviewed by the BoilerFaultCodes Editorial Team Last reviewed 27 April 2026

Fault code E785 appears across 1 boiler brand and 6 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 accurately measure the water flow or pressure inside the system, which is preventing it from heating your home safely. (As reported on Navien NCB)

Pick your boiler brand for the E785 fix

Navien E785 6 models

Source

Information for the E785 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