BoilerFaultCodesYour boiler is struggling to move water around correctly, often caused by a lack of pressure or air trapped in the system.
Book a Gas Safe engineer within 24–48 hours. Your boiler may be unsafe or could break down completely if left.
Technical description: All Boilers
What causes this fault?
This fault occurs when the boiler detects that water is not circulating quickly enough through the main heat exchanger, which can lead to overheating. It is usually caused by low water pressure, a buildup of air bubbles within the pipes, or a pump that has become stuck or damaged. Essentially, the system has stopped to prevent itself from getting too hot because the heat isn't being carried away effectively.
This issue often appears when the heating is first switched on after summer, as the internal pump can seize or air can settle in the system during long periods of inactivity.
DIY fix possible
Check the pressure gauge and top it up to 1.5 bar if it is too lowBleed your radiators to remove any trapped airEnsure all radiator valves and isolation valves are fully open
Find a Gas Safe engineer
Search the official register for a qualified engineer in your area.
Gas Safe Register →Protect yourself from future repair bills
A boiler cover plan would cover faults like 1p1 — no call-out fees, no surprises.
Affiliate links — we may earn a commission at no extra cost to you.
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.
Affiliate links — we may earn a commission at no extra cost to you.