BoilerFaultCodesYour boiler has detected that the water pressure is too low for it to operate safely, which is usually caused by a small leak or air in the system.
Book a Gas Safe engineer within 24–48 hours. Your boiler may be unsafe or could break down completely if left.
Technical description: Insufficient water pressure, Air in boiler, or the pressure in the boiler is low.
What causes this fault?
This fault occurs when the internal water pressure drops below the minimum level required for the boiler to circulate heat safely. The most common reason is a small leak in the radiator network or air being released through the valves, which gradually reduces the volume of water in the system.
This issue often surfaces when the heating is turned back on for autumn, as the transition from cold to hot water can expose minor leaks or highlight air trapped in the radiators.
DIY fix possible
Check the pressure gauge on the front of the boiler; it should ideally be between 1 and 1.5 bar.Locate the external filling loop (the silver flexible hose) underneath or near the boiler.Slowly open the valves on the filling loop until you hear water entering and the needle reaches 1.5 bar, then close them tightly.
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A boiler cover plan would cover faults like 04 — no call-out fees, no surprises.
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Parts for discontinued models can be hard to find and expensive. A new A-rated boiler could save you money on both repairs and energy bills.
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