How much does it cost to fix boiler error code A1?

Typical repair cost for the boiler A1 fault is £180-£350 including labour.

A1 High

Boiler Fault Code A1

Reviewed by the BoilerFaultCodes Editorial Team Last reviewed 27 April 2026

Fault code A1 appears across 3 boiler brands and 31 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 there is not enough water circulating through the system, which could be due to a leak or a mechanical issue with the pump. (As reported on Worcester Bosch CDi Classic)

Pick your boiler brand for the A1 fix

Atag A1 2 models Viessmann A1 1 model Worcester Bosch A1 28 models

Source

Information for the A1 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