BoilerFaultCodesYour boiler has become too hot or water is not moving through the system properly, causing the unit to shut down for safety.
Book a Gas Safe engineer within 24–48 hours. Your boiler may be unsafe or could break down completely if left.
Technical description: Flow temperature overheat or no water flow
What causes this fault?
This fault occurs when the water inside your boiler reaches a temperature that is too high for safe operation. It is usually caused by a blockage in the pipework or a mechanical failure in the pump, which prevents water from moving away from the heat source quickly enough. In some cases, a buildup of debris or sludge in the system can restrict flow and trigger this safety shutdown.
This fault is more common in autumn when heating is turned back on after the summer, as internal pump parts can seize from lack of use.
DIY fix possible
Check that your radiator valves are fully openEnsure your boiler pressure is between 1.0 and 1.5 barBleed your radiators to remove any trapped air
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 L1 — 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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