BoilerFaultCodesWorcester Bosch 1-b2 Fault Code
Also written as 1B2 — same fault.
The Worcester Bosch 1-b2 fault code means: your boiler has detected that hot water is being drawn through the system, often serving as an advisory notification rather than a breakdown.. It appears on 1 Worcester Bosch model in our database.
Technical description: DHW flow rate: Hot water flow rate.
What causes the Worcester Bosch 1-b2 fault?
This code is triggered when the boiler's internal sensor detects water moving through the hot water pipes, even if you haven't turned on a tap. It often occurs due to a 'passing' tap that isn't fully shut off, a minor leak in the pipework, or a sensor that has become overly sensitive or faulty. Effectively, the boiler is simply notifying you that it is working to heat water because it believe there is a demand.
DIY fix possible
Check that all hot water taps in the property are fully closedInspect for any dripping taps or leaking shower headsMonitor the display to see if the code clears once water usage stops
Find a Gas Safe engineer
Search the official register for a qualified engineer in your area.
Gas Safe Register →Worcester Bosch models that show the 1-b2 fault code
Click a model for the full fault code list and model-specific repair notes.
Source
Worcester Bosch 1-b2 fault code information on this page is sourced and cross-checked against the official Worcester Bosch service / installation manuals for each affected model.
Reviewed by the BoilerFaultCodes Editorial Team · Last reviewed 27 April 2026