BoilerFaultCodesYour heating system is losing water through a leak, causing the pressure to drop too low for the boiler to operate safely.
Book a Gas Safe engineer within 24–48 hours. Your boiler may be unsafe or could break down completely if left.
Technical description: 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 then a water leak is indicated. DO NOT FIRE THE BOILER IF THE PRESSURE HAS REDUCED TO ZERO FROM THE ORIGINAL SETTING.
What causes this fault?
This fault occurs when water escapes from the sealed pipework, causing the internal pressure to drop below the level needed for the boiler to pump heat around your home. The most common reasons are a slow leak from a radiator valve, a perished seal inside the boiler, or a failing expansion vessel that can no longer regulate system pressure.
This issue is frequently noticed in autumn when the heating is turned on for the first time after summer, as the change in temperature and pressure can expose weakened seals or small weep leaks.
DIY fix possible
Locate the external filling loop (usually a silver braided hose with two small valves).Slowly open both valves to top up the water until the pressure gauge needle matches the red set point.Ensure both valves are tightly closed once the pressure is restored.
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