BoilerFaultCodesYour boiler has detected that hot water isn't moving through the system properly, which is causing it to shut down to prevent overheating.
Book a Gas Safe engineer within 24–48 hours. Your boiler may be unsafe or could break down completely if left.
Technical description: Primary water circulation error
What causes this fault?
This fault occurs when the water inside the boiler gets too hot too quickly because it isn't being pumped away effectively. The most common reasons are a seized internal pump, a physical blockage in the pipework, or air trapped within the system preventing proper flow. It can also be triggered if there isn't enough water pressure to allow the circulation to take place.
This fault is more frequent in autumn when heating systems are first turned on after being idle all summer, which can cause the internal pump to seize.
DIY fix possible
Check that your system pressure is between 1 and 1.5 bar on the pressure gauge.Ensure all radiator valves and any isolation valves under the boiler are fully open.Listen for air trapped in the system and bleed your radiators if necessary.
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A boiler cover plan would cover faults like E125 — 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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