BoilerFaultCodesYour boiler has detected that the water is flowing in the wrong direction through the pipes or that the temperature sensors have been installed on the wrong pipes.
Book a Gas Safe engineer within 24–48 hours. Your boiler may be unsafe or could break down completely if left.
Technical description: Flow/Return Reversed
What causes this fault?
This fault occurs when the boiler detects that heat is rising on the return pipe faster than the flow pipe, suggesting the water is moving backwards. It is often caused by a failing internal pump that can no longer push water in the right direction or faulty sensors that are sending incorrect temperature readings to the control board.
This issue often surfaces when the heating is first turned on in autumn, as pumps can seize or become sluggish after being inactive throughout the summer.
Engineer required
This fault requires a Gas Safe registered engineer. Do not attempt gas-related repairs yourself.
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A boiler cover plan would cover faults like F 0A — 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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