BoilerFaultCodesYour boiler has detected that the water pressure in the system is too low to operate safely and has shut down to protect itself.
Book a Gas Safe engineer within 24–48 hours. Your boiler may be unsafe or could break down completely if left.
Technical description: Check system pressure – refill if necessary. If fault reoccurs, contact a heating engineer.
What causes this fault?
This fault occurs when the internal sensor detects that there isn't enough water volume within the central heating circuit to safely transfer heat. The most common reasons are a slow leak from a radiator valve or the pressure dropping naturally after you have recently bled air from your radiators.
This fault is frequent in autumn when homeowners turn their heating back on for the first time and find the pressure has dropped over the summer months.
DIY fix possible
Locate the filling loop (usually a silver flexible hose) underneath or near the boiler.Slowly open the one or two taps/valves on the filling loop until you hear water moving.Watch the pressure gauge and close the taps firmly once the needle reaches between 1.0 and 1.5 bar.Press the 'Reset' button on the boiler control panel to clear the error.
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 AL41 — 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.