BoilerFaultCodesYour heating system is losing water, which means there is likely a leak or a failing pressure relief valve causing the boiler to stop working correctly.
Book a Gas Safe engineer within 24–48 hours. Your boiler may be unsafe or could break down completely if left.
Technical description: Indicated if the red arrow on the system pressure gauge is set above zero and the system pressure is seen to fall below this value over a period of time, indicating a water leak.
What causes this fault?
This fault occurs when the sealed system no longer has enough water to circulate heat safely, triggered by a physical escape of water from the pipework or components. The most common reasons are a weeping connection on a radiator valve or a internal part like the expansion vessel failing, which forces water out through the safety discharge pipe.
This issue often comes to light in autumn when the heating is first turned on, as the increased heat and pressure stress seals that may have perished over the summer.
DIY fix possible
Check all visible radiator valves and pipework for signs of wet patches or stains.Locate the filling loop (a silver flexible hose) and carefully top up the pressure until the gauge needle matches the red marker.Run the heating and re-check for leaks if the pressure drops again immediately.
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 Loss of system water pressure — no call-out fees, no surprises.
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