BoilerFaultCodesYour boiler has detected that the water pressure in the system is too low and needs to be topped up to work properly.
Book a Gas Safe engineer within 24–48 hours. Your boiler may be unsafe or could break down completely if left.
Technical description: Low Water Pressure
What causes this fault?
This fault occurs when the water level inside your central heating system drops below a safe threshold, often due to a small leak in a radiator valve or air escaping through the vents. Without enough water pressure, the boiler cannot safely circulate heat around your home and shuts down to prevent internal damage. The most common reason is the natural loss of pressure over time or after you have recently bled your radiators.
This issue is frequently seen in autumn when homeowners turn their heating back on for the first time after summer, revealing pressure losses that occurred while the system was idle.
DIY fix possible
Locate the filling loop (the flexible silver hose) underneath your boiler.Slowly open the blue-handled valves until you hear water entering the system.Watch the pressure gauge and close the valves tightly once the needle reaches 1.5 bar.
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 4.11 — 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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