BoilerFaultCodesYour boiler is struggling with water flow, likely due to a build-up of debris or air in the system which is preventing the heat from circulating properly.
This fault should be looked at by a Gas Safe engineer within the next week or two. It may get worse if left.
Technical description: Not relevant
What causes this fault?
This fault occurs when the boiler's internal temperature rises too quickly because the heated water cannot move away from the heat exchanger fast enough. The most common cause is a blockage from sludge or trapped air pockets that restrict the flow, forcing the boiler to throttle back or stop to prevent overheating.
This issue often surfaces in autumn when the heating is turned on for the first time after summer, as settled debris in the pipes can shift and block the pump.
DIY fix possible
Check that all radiator valves are fully openBleed your radiators to remove any trapped airEnsure the boiler pressure is between 1.0 and 1.5 bar on the gauge
Find a Gas Safe engineer
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A boiler cover plan would cover faults like D.24 — no call-out fees, no surprises.
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