BoilerFaultCodesYour boiler has stopped working because it cannot detect water moving through the system to keep it from overheating.
Book a Gas Safe engineer within 24–48 hours. Your boiler may be unsafe or could break down completely if left.
Technical description: No Water Flow
What causes this fault?
This fault occurs when the boiler's internal sensors detect that water isn't moving through the unit quickly enough to safely carry heat away. The most common reasons are a seized internal pump, a significant blockage in the pipework, or a faulty sensor providing an incorrect reading to the control board.
This issue often surfaces during the first cold spell of autumn when a pump that has been sitting idle all summer fails to restart.
DIY fix possible
Check if the pressure gauge is below 1 bar and top it up using the filling loopEnsure all radiator valves and boiler isolation valves are fully openCheck for any visible leaks around your radiators or the boiler itselfRestart the boiler once the pressure is correct
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 4.12 — 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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