BoilerFaultCodesYour boiler has detected that there is too much water in the system, which puts extra stress on the pipes and components.
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 > 2,9 bar
What causes this fault?
This fault occurs when the internal water pressure exceeds a 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 lost its air charge. In some cases, a faulty heat exchanger can allow fresh mains water to leak into the heating circuit, causing the pressure to rise continuously.
This issue often surfaces when the heating is first turned on for winter, as the expansion of warming water puts extra stress on a system that might already be overfilled or have a failing expansion vessel.
DIY fix possible
Locate a radiator bleed valve and use a key to release water into a container until the pressure gauge on the boiler drops to 1.5 bar.Ensure the external filling loop valves are tightly closed.Check if the filling loop hose is disconnected to prevent further water entering the system.
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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