BoilerFaultCodesYour boiler is struggling to push water around the system, often due to a blockage in narrow pipes or a pump that isn't working correctly.
Book a Gas Safe engineer within 24–48 hours. Your boiler may be unsafe or could break down completely if left.
Technical description: Microbore system or pump flow rate issue
What causes this fault?
This fault happens 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 failing internal pump that no longer has the power to push the water, or a buildup of debris and limescale blocking the narrow internal pipework. Because the water stays in the boiler for too long, it overheats and triggers a safety shutdown.
This issue often comes to light during the first cold spell of autumn when the heating is turned back on after being dormant all summer, causing stuck pumps to fail or settled sludge to shift and cause blockages.
Engineer required
This fault requires a Gas Safe registered engineer. Do not attempt gas-related repairs yourself.
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