BoilerFaultCodesYour boiler has detected that water is not circulating correctly through the main heat exchanger, often caused by a blockage or a pump issue.
Book a Gas Safe engineer within 24–48 hours. Your boiler may be unsafe or could break down completely if left.
Technical description: Primary flow fault
What causes this fault?
This fault occurs when water is unable to move through the boiler's heat exchanger quickly enough to safely carry heat away. The most common reasons are a failing circulation pump that can no longer push the water, or a physical blockage caused by a build-up of sludge and debris within the system pipework.
This issue frequently appears during the first cold spell of autumn when the heating is turned back on after being idle all summer, which can cause internal pump parts to seize.
Engineer required
This fault requires a Gas Safe registered engineer. Do not attempt gas-related repairs yourself.
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A boiler cover plan would cover faults like E154 — 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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