BoilerFaultCodesYour boiler has detected that the water pressure inside the system is too high, which could cause leaks or damage if not reduced.
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 greater than 2.9 bar
What causes this fault?
This fault occurs when the internal water pressure exceeds safe operating limits, often because the manual filling loop has been left slightly open or has a slow leak. It can also be caused by a failure in the expansion vessel, which is the part responsible for managing water expansion as it heats up. Without space for the water to expand, the pressure rises rapidly until the boiler shuts down to prevent internal damage.
This issue often surfaces in winter when the heating is first turned on for long periods, as the constant heating and cooling of water exposes faults in the expansion vessel.
DIY fix possible
Locate a radiator bleed valve and use a key to release water into a cloth or container.Monitor the boiler pressure gauge until it drops back into the green zone (typically 1.2 to 1.5 bar).Ensure the silver braided filling loop valves are fully closed and not accidentally left open.
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 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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