The system water pressure is too low (or there is no water), so the boiler has shut down to protect itself.
Most common on: ecoTEC plus, ecoTEC pro
F.22 is one of the most common Vaillant fault codes. It means the boiler has detected too little water in the sealed heating system — usually low pressure, sometimes a genuine lack of water reaching the pump and heat exchanger. Firing without enough water would let the heat exchanger overheat, so the boiler stops.
Low pressure is often simple to fix by topping up with the filling loop. But pressure that keeps dropping points to a leak or a failed expansion vessel, and F.22 that returns after the correct pressure is restored can indicate a pump or sensor problem rather than a real lack of water.
Check the pressure gauge or display. If it reads below about 1 bar, the system needs topping up.
Open the filling loop slowly until the gauge reads about 1.0–1.5 bar (cold), then close it fully and reset the boiler.
After topping up, press the reset button. If the boiler fires and F.22 clears, it was simply low pressure.
If the pressure keeps falling, there is a leak or an expansion vessel fault — book an engineer rather than topping up repeatedly.
If pressure is correct but F.22 returns, the pump or pressure sensor may be at fault — this needs a Gas Safe engineer to diagnose.
Work on the gas side of a boiler must be carried out by a Gas Safe registered engineer. The checks above are limited to safe, non-invasive things a homeowner can look at (pressure, resets, the gas supply) — if in doubt, stop and call an engineer.
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The system water pressure is too low (or there is no water), so the boiler has shut down to protect itself. F.22 is one of the most common Vaillant fault codes. It means the boiler has detected too little water in the sealed heating system — usually low pressure, sometimes a genuine lack of water reaching the pump and heat exchanger. Firing without enough water would let the heat exchanger overheat, so the boiler stops.
Often yes — this one is frequently resolved by a homeowner. Check the pressure gauge or display. If it reads below about 1 bar, the system needs topping up. If it keeps coming back, book a Gas Safe registered engineer.
A recurring F.22 means the underlying cause has not been fixed — most often low system pressure (typically below about 1 bar). Resetting repeatedly will not solve it; get the boiler diagnosed properly.