BoilerFaultCodesYour boiler has detected that there is too much water in the system, causing the internal pressure to rise above safe operating levels.
Turn off your boiler and stop using gas appliances. Call a Gas Safe engineer now — this fault can be dangerous if ignored.
Technical description: Water pressure too high. The system pressure is too high.
What causes this fault?
This fault occurs when the water pressure inside your heating system exceeds the safe limit, often because the filling loop used to top up the system has been left slightly open or is leaking. It can also happen if the expansion vessel, which manages heat-related pressure changes, has failed or if the system has been significantly overfilled during recent maintenance.
This fault is more common in autumn when homeowners top up their system pressure ahead of the heating season and accidentally add too much water.
DIY fix possible
Locate a radiator and use a bleed key to release water into a container until the pressure gauge on the boiler drops to 1.5 bar.Check that the internal or external filling loop valves are fully closed and not accidentally left open.If the pressure continues to rise after bleeding, turn off the mains water supply and call an engineer.
Find a Gas Safe engineer
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A boiler cover plan would cover faults like S.41 — 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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