The boiler detected that the system water pressure has dropped below its working limit and shut itself down for safety.
What is error F.22?
On Vaillant Combi Boiler units, code F.22 means low water pressure. The boiler detected that the system water pressure has dropped below its working limit and shut itself down for safety.
Likely causes
- A small leak in the pipework or radiators
- Pressure loss after bleeding the radiators
- Water discharging from the safety valve or an expansion vessel fault
Safe steps you can take
- Read the pressure on the gauge under the boiler.
- Slowly open the filling loop and bring the pressure to the value in your manual (usually 1–1.5 bar), then close it.
- Reset the boiler and watch the pressure for a few days.
If pressure keeps dropping there is a leak; topping up again and again will not fix it — call a technician.
Video guide
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Watch on YouTubeFrequently asked questions
Is error F.22 dangerous?
Usually not; the unit stopped to protect itself. If the code returns after the steps, call a technician.
Is a reset enough?
One reset clears temporary causes. If the code comes back, the real cause remains — don't keep resetting.
How much does the repair cost?
It depends on the part. After diagnosis the service sends the price to your tracking link; nothing is done without your approval.
Is the repair guaranteed?
Services on the platform write the warranty for parts and labour on the service form, which is sent to you as a PDF.
Sources: tesisat.org — Kombi arıza kodları . Code meanings can vary by model; check your user manual.