BoilerFaultCodesYour boiler is struggling to move hot water around the system, which is usually caused by a blockage or a pump issue that is preventing the unit from cooling itself down.
Book a Gas Safe engineer within 24–48 hours. Your boiler may be unsafe or could break down completely if left.
Technical description: Circulation error
What causes this fault?
This fault occurs when the boiler detects that water is not moving through the system quickly enough to carry heat away from the burner. The most common reasons are a failed internal pump that can no longer push the water, or a build-up of debris and sludge that has physically blocked the pipes or heat exchanger. Effectively, the boiler shuts down because it is getting too hot too quickly and needs to prevent internal damage.
This fault is more common in autumn and winter when the heating is first switched back on, as debris often settles and solidifies during the summer months when the pump is inactive.
DIY fix possible
Check that all radiator valves are fully openEnsure the boiler pressure is between 1.0 and 1.5 bar on the gaugeGently bleed air from your radiators using a radiator key
Find a Gas Safe engineer
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Gas Safe Register →Protect yourself from future repair bills
A boiler cover plan would cover faults like E125 — 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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