BoilerFaultCodes Block 11 Medium
Boiler Fault Code Block 11
Also written as BLOCK11 — same fault.
Reviewed by the BoilerFaultCodes Editorial Team Last reviewed
Fault code Block 11 appears across 1 boiler brand and 4 models. The exact meaning varies by manufacturer — pick your boiler brand below to see the model-specific fix.
Most common meaning Your boiler has temporarily stopped heating your home because the water is not circulating fast enough to transfer heat away, likely due to a blockage in your pipes or radiators. (As reported on Atag Q 25CR)
Pick your boiler brand for the Block 11 fix
Source
Information for the Block 11 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