BoilerFaultCodesYour boiler has shut down because it has detected an internal safety issue, likely related to overheating or a lack of water circulation.
Book a Gas Safe engineer within 24–48 hours. Your boiler may be unsafe or could break down completely if left.
Technical description: The safety devices have been activated (lockout)
What causes this fault?
This fault occurs when the boiler's internal sensors detect that the water temperature has risen too quickly or peaked beyond safe limits. The most common reason is a failure in the circulation pump or a blockage in the heat exchanger, preventing heat from being moved away from the burner. It can also be triggered if there is air trapped in the system or if the water pressure has dropped too low to function.
This issue often surfaces during the first cold spell of autumn when a pump that has been idle all summer fails to restart correctly.
DIY fix possible
Check if the system water pressure is between 1 and 1.5 bar on the pressure gaugeIf the pressure is low, use the filling loop to top it up to the correct levelAttempt to reset the boiler by turning the selector switch to the reset position and back
Find a Gas Safe engineer
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Gas Safe Register →Protect yourself from future repair bills
A boiler cover plan would cover faults like E25 — no call-out fees, no surprises.
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Could it be time for a new boiler?
If repair costs are adding up, a new energy-efficient boiler could be the smarter long-term choice.
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