BoilerFaultCodesYour boiler is struggling to move water around the system, often because the water level is too low or something is blocking the flow.
Book a Gas Safe engineer within 24–48 hours. Your boiler may be unsafe or could break down completely if left.
Technical description: Low water / Pump Failure / Blockage
What causes this fault?
This fault occurs when the boiler detects a sudden, sharp rise in temperature because the heated water isn't moving away from the burner quickly enough. The most common reasons are a lack of water pressure in the system, a pump that has seized up, or a physical blockage like sludge or debris preventing circulation.
This issue is more frequent in autumn when heating systems are turned back on after being idle all summer, which can cause the internal pump to stick.
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 low, use the filling loop valves underneath the boiler to top it up.Ensure all radiator valves are fully open to allow water to flow freely.
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A boiler cover plan would cover faults like F.24 — no call-out fees, no surprises.
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Parts for discontinued models can be hard to find and expensive. A new A-rated boiler could save you money on both repairs and energy bills.
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