What it means
Vaillant's VWZ AI operating instructions show this as F.22, alternating with the current pressure on the display, while the fault table lists it as F.022. A warning, M32, appears first when the pressure drops below 0.7 bar. F.22 goes out once the pressure is back above 0.5 bar.
What to check, in order
- Read the pressure
Vaillant's operating instructions say it should be 1.0 to 1.5 bar with the system cold, and may need to be higher in a building with several storeys. You can see it through the Live Monitor menu on the display.
- Ask your installer to top it up
Vaillant's manual tells you to inform a competent person so they can top up the heating water. Their fix is to top up and then purge the air out.
- Look for signs of a leak
Vaillant lists leaks and air pockets as the causes of the pressure loss. Check around radiators and visible pipework for drips or damp patches.
- Don't just keep topping up
The manual says that if the pressure drops often, the reason for the loss has to be found and fixed.
When to call your installer
If the pressure won't stay up, call your installer. Vaillant's fault table has the engineer check for leaks, top up and purge the system, and replace the pressure sensor if it is faulty. Vaillant's fault code page also lists faulty wiring to the pressure sensor, a pump problem, a faulty fill valve or a faulty internal expansion vessel.
Quick answers
What does the Vaillant aroTHERM F022 error code mean?
The water pressure in your heating system, which Vaillant calls the building circuit, has fallen below 0.5 bar for more than a minute. Vaillant's VWZ AI operating instructions show this as F.22, alternating with the current pressure on the display, while the fault table lists it as F.022. A warning, M32, appears first when the pressure drops below 0.7 bar. F.22 goes out once the pressure is back above 0.5 bar.
Can I fix Vaillant aroTHERM F022 myself?
Easy (about 10 minutes to check). Start with: read the pressure; ask your installer to top it up; look for signs of a leak. If the pressure won't stay up, call your installer. Vaillant's fault table has the engineer check for leaks, top up and purge the system, and replace the pressure sensor if it is faulty. Vaillant's fault code page also lists faulty wiring to the pressure sensor, a pump problem, a faulty fill valve or a faulty internal expansion vessel.
Is Vaillant aroTHERM F022 worth repairing?
Worth fixing. A top-up and purge usually clears it. If the pressure keeps falling, a leak or a faulty part needs finding.
Checked against
- Vaillant heat pump appliance interface VWZ AI (for aroTHERM plus VWL ..5/6 A): operating and installation instructions (PDF, 0020291573_01)
- Vaillant: heat pump fault codes
Last reviewed October 2026. Manufacturers update their pages, and your manual is the final word. Spotted a mistake? Email contact@appliance-error-codes.com.