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 the return pipe is hotter than the flow pipe, suggesting the water is moving backwards through the unit. It is often caused by a failing internal pump that cannot push water in the right direction, or by the temperature sensors becoming faulty and sending incorrect readings to the control board.
Engineer required
This fault requires a Gas Safe registered engineer. Do not attempt gas-related repairs yourself.
Find a Gas Safe engineer
Search the official register for a qualified engineer in your area.
Gas Safe Register →Protect yourself from future repair bills
A boiler cover plan would cover faults like FA — no call-out fees, no surprises.
Affiliate links — we may earn a commission at no extra cost to you.
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.
Affiliate links — we may earn a commission at no extra cost to you.