BoilerFaultCodesYour boiler is struggling to move water around 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 circuit error circulation fault
What causes this fault?
This fault occurs when the boiler detects that water is not moving through the internal pipes quickly enough to take the heat away from the burner. The most common reasons are a failed pump that can no longer push the water, or a blockage caused by a build-up of sludge and debris in the system. Because the heat cannot escape, the boiler shuts down as a safety precaution to prevent the internal components from melting or cracking.
This fault often appears during the first cold snap of autumn when a heating system that has been sitting idle all summer is suddenly forced to move heavy, settled sludge.
DIY fix possible
Check that all radiator valves (TRVs) are fully openEnsure your system pressure is between 1.0 and 1.5 bar on the gaugeTry resetting the boiler to see if the error clears
Find a Gas Safe engineer
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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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