BoilerFaultCodesYour boiler has sensed that water is not moving through the system properly, which is causing it to shut down to prevent overheating.
Book a Gas Safe engineer within 24–48 hours. Your boiler may be unsafe or could break down completely if left.
Technical description: Water circulation fault
What causes this fault?
This fault occurs when the boiler detects a significant temperature difference between the water leaving the unit and the water returning to it, suggesting a blockage or pump failure. The most common reason is a seized or failing circulation pump that can no longer push water through the radiators and pipework. Additionally, a build-up of sludge or limescale within the heat exchanger can restrict flow enough to trigger this safety shutdown.
This fault is more common in autumn when heating is turned on for the first time after summer, as pumps are prone to seizing during long periods of inactivity.
DIY fix possible
Check that the boiler pressure is between 1 and 1.5 bar on the displayEnsure all radiator valves are fully openListen for air in the system and bleed radiators if necessary
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A boiler cover plan would cover faults like F23 — 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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