BoilerFaultCodesYour boiler has detected that water is not circulating properly through the system, often caused by a lack of water pressure or a blockage.
Book a Gas Safe engineer within 24–48 hours. Your boiler may be unsafe or could break down completely if left.
Technical description: All Boilers
What causes this fault?
This fault occurs when the boiler detects that heat is building up too quickly because water isn't moving through the unit as it should. The most common reasons are a lack of water pressure in the system, a pump that has become stuck or failed, or a buildup of debris and limescale that is restricting the flow.
This issue is more common in autumn when homeowners turn their heating back on for the first time after summer, often revealing pumps that have seized or air trapped in the radiators.
DIY fix possible
Check the pressure gauge on the front of the boiler; it should be between 1 and 1.5 bar.If the pressure is low, use the filling loop underneath the boiler to top it up until the needle reaches 1.2 bar.Bleed your radiators using a radiator key to release any trapped air, then re-check the pressure gauge.
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A boiler cover plan would cover faults like 103 — 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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