BoilerFaultCodesYour boiler has stopped working because the water isn't moving through the system correctly, which is often caused by air bubbles or a blockage.
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, indicating that heat is not being carried away fast enough. The most common reasons are a failing internal pump that can't push the water around, or a build-up of sludge and debris that has created a physical blockage in the pipework. It can also be triggered by a large pocket of air trapped within the heat exchanger, preventing smooth water flow.
This issue often surfaces in autumn when the heating is turned on for the first time in months, as pump components can seize up or debris can settle during the summer period.
DIY fix possible
Check that all radiator valves and isolation valves are fully openBleed your radiators to remove trapped air from the systemCheck the boiler pressure gauge and top it up to 1.5 bar if it is too low
Find a Gas Safe engineer
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A boiler cover plan would cover faults like F23 — no call-out fees, no surprises.
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