BoilerFaultCodesYour boiler has sensed that the pump is running but the water isn't moving through the system properly, causing it to shut down to prevent damage.
Book a Gas Safe engineer within 24–48 hours. Your boiler may be unsafe or could break down completely if left.
Technical description: Pump / water shortage (no pressure increase when pump is starting)
What causes this fault?
This fault occurs when the boiler's internal computer fails to detect a small required rise in water pressure when the pump starts up. The most common reasons are a pressure sensor that has become blocked with system sludge or a pump that has seized and is no longer moving water through the heat exchanger.
This fault is frequently seen in autumn when the heating is turned back on for the first time, as pumps can seize after being idle throughout the summer months.
DIY fix possible
Check the pressure gauge on the front of the boiler; it should be between 1.0 and 1.5 bar.If the pressure is too low, use the external filling loop to top up the system water.Ensure all radiator valves and internal isolation valves are fully open.
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A boiler cover plan would cover faults like F.75 — no call-out fees, no surprises.
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