What it means
On ecoTEC plus and ecoTEC pro boilers the display switches between F.22 and the current pressure. The newest ecoTEC plus shows F.022.
What to check, in order
- Read the pressure gauge
With the system cold, Vaillant's ecoTEC plus manual wants 1.0 to 2.0 bar. The boiler switches off if the pressure falls below 0.5 bar.
- Top up with the filling loop
Open all the radiator valves first. Then open the filling tap slowly and let water in until the gauge reaches the right pressure, and close it again. Follow the instructions for your type of filling loop.
- Bleed the radiators, then check again
Vaillant's manual says to bleed the radiators after filling and then check the pressure once more.
- Look for a leak if it keeps dropping
Damp spots or rust marks around radiators, flaking wallpaper and bubbling skirting boards are the signs Vaillant mentions.
When to call a Gas Safe engineer
If the filling loop doesn't raise the pressure, or you find signs of a leak, call a Gas Safe registered engineer.
Good to know
- Vaillant's figures differ a little between editions. The 2023 ecoTEC plus manual recommends at least 1 bar and says to top up below 0.8 bar. Its advice pages mention around 1.5 bar with the system cold. Your boiler's manual is the final word.
Parts people end up buying
Only if the checks above point to a part. Match it to your model number first: it's on a label on the data badge, usually under the boiler or behind the front cover.
- Radiator bleed keySearch on Amazon
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Quick answers
What does the Vaillant F22 fault code mean?
The water pressure in your heating system has dropped too low, so the boiler has shut down for now. On ecoTEC plus and ecoTEC pro boilers the display switches between F.22 and the current pressure. The newest ecoTEC plus shows F.022.
Can I fix Vaillant F22 myself?
Easy (about 15 minutes). Start with: read the pressure gauge; top up with the filling loop; bleed the radiators, then check again. If the filling loop doesn't raise the pressure, or you find signs of a leak, call a Gas Safe registered engineer.
Is Vaillant F22 worth repairing?
Usually free. Topping up the pressure clears it. If it keeps falling, water is escaping somewhere and needs finding.
Checked against
- Vaillant ecoTEC plus VU, VUW, VUI ..6/5-5 operating instructions (PDF)
- Vaillant ecoTEC plus operating instructions, 2023 edition (PDF)
- Vaillant: what to do if your boiler has no pressure
Last reviewed October 2026. Manufacturers update their pages, and your manual is the final word. Spotted a mistake? Email contact@appliance-error-codes.com.