BoilerFaultCodesWorcester Bosch E5218 Fault Code
The Worcester Bosch E5218 fault code means: your boiler has shut down because the internal water temperature has become too hot, likely due to a lack of water flow or a circulation problem.. It appears on 2 Worcester Bosch models in our database.
Technical description: Flow temperature too high
What causes the Worcester Bosch E5218 fault?
This fault occurs when the water inside the boiler heats up too quickly or reaches an unsafe temperature, forcing the system to shut down for safety. The most common reason is a failure in the circulation pump or a blockage in the pipes, which prevents the hot water from moving away from the burner. It can also be caused by a faulty sensor that is incorrectly reporting the water temperature to the control board.
This issue often appears when the heating is first turned on after summer, as circulation pumps can seize up if they haven't been used for several months.
DIY fix possible
Check if all radiator valves are open to ensure water can flow.Check the boiler pressure gauge and top up to 1.5 bar if it is too low.Restart the boiler using the reset button to see if the fault clears.
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Gas Safe Register →Worcester Bosch models that show the E5218 fault code
Click a model for the full fault code list and model-specific repair notes.
Source
Worcester Bosch E5218 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