BoilerFaultCodesWorcester Bosch 2.5 Fault Code
Also written as 25 — same fault.
The Worcester Bosch 2.5 fault code means: your boiler has detected that the water inside is getting too hot and has temporarily switched itself off to prevent damage.. It appears on 5 Worcester Bosch models in our database.
Technical description: Service Function: Max. CH flow temperature
What causes the Worcester Bosch 2.5 fault?
This fault occurs when the water inside the boiler gets too hot too quickly, causing the system to shut down for safety. The most common reasons are a lack of water flow caused by a sticking pump or a sensor that has become faulty and is giving a false temperature reading. It can also happen if air is trapped in the heat exchanger or if the system is partially blocked with debris.
This fault is more common in autumn when homeowners first turn their heating back on after summer, as pump components can seize up during long periods of inactivity.
Engineer required
This fault requires a Gas Safe registered engineer. Do not attempt gas-related repairs yourself.
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 2.5 fault code
Click a model for the full fault code list and model-specific repair notes.
Source
Worcester Bosch 2.5 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