BoilerFaultCodesYour boiler has detected that there is not enough water pressure in the system to operate safely, causing it to shut down to prevent overheating.
Book a Gas Safe engineer within 24–48 hours. Your boiler may be unsafe or could break down completely if left.
Technical description: Dry fire / Low water in system / Overheat
What causes this fault?
This fault occurs when the boiler's internal sensor detects that the system pressure has dropped too low for the unit to heat water safely. The most common reason is a slow leak somewhere in your radiator network or a faulty expansion vessel that can no longer regulate pressure correctly. Without enough water to circulate, the boiler shuts down to prevent the heat exchanger from overheating or sustaining permanent damage.
This fault is more common in autumn and winter when the heating is first turned on, as the increased pressure of hot water can expose small leaks or reveal that the system lost pressure while sitting idle during the summer.
DIY fix possible
Locate the silver braided filling loop hoses underneath or near the boiler.Open the two small valves on the filling loop to allow water into the system.Watch the pressure gauge on the front of the boiler until it reaches between 1.0 and 1.5 bar, then close both valves tightly.
Find a Gas Safe engineer
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A boiler cover plan would cover faults like F.22 — no call-out fees, no surprises.
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Vaillant Turbomax Plus 824/828E is discontinued — time for a new one?
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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