BoilerFaultCodesYour boiler has reached a critically high water pressure that is unsafe for continued operation.
Turn off your boiler and stop using gas appliances. Call a Gas Safe engineer now — this fault can be dangerous if ignored.
Technical description: If the pressure indicated at normal working temperatures (80 °C) shows 'P 3.1 or higher, switch off the boiler and contact your service engineer.
What causes this fault?
This fault occurs when the water inside your central heating system expands beyond the capacity of the boiler's safety limits. The most common reason is a failure of the internal expansion vessel or a filling loop tap that has been left slightly open, causing the pressure to rise until it becomes unsafe. Because the boiler cannot safely vent this excess pressure, it shuts down to prevent damage to the internal seals and pipework.
This fault often appears when you turn your heating back on for the first time in autumn, as the thermal expansion of cold water puts immediate stress on a weakened expansion vessel.
DIY fix possible
Locate a radiator bleed valve and use a key to release water into a jug until the pressure drops below 1.5 bar on the display.Ensure the external filling loop valves are tightly closed.If the pressure rises again immediately, turn off the boiler and call an engineer.
Find a Gas Safe engineer
Search the official register for a qualified engineer in your area.
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A boiler cover plan would cover faults like P 3.1 — no call-out fees, no surprises.
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