BoilerFaultCodesYour boiler has detected that water is not circulating correctly before the burner lights, which usually means there is 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: Pre-circulation fault
What causes this fault?
This fault occurs when the boiler's internal sensors detect that water isn't moving through the unit quickly enough before the flames ignite. The most common reasons are a seized central heating pump that can't push the water around, or a build-up of sludge and debris creating a physical blockage in the heat exchanger.
This issue often appears at the start of autumn when the heating is turned back on after being idle all summer, which can cause the pump to stick.
DIY fix possible
Ensure your radiator valves are open to allow water flowCheck that the boiler pressure is between 1 and 1.5 bar on the gaugeRestart the boiler by pressing the reset button for five seconds
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 E109 — 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.