How F22 shows up
- The gauge reads close to 0
- Heating won't start, or stops shortly after
- Radiators stay cold
- Hot water keeps working normally
- Code F22 appears after the boiler has been off for a long time
What error code F22 means
- Pressure too low — the heating circuit is short of water, the boiler shuts down as a safety measure to avoid running dry.
- Recent bleeding — after bleeding a radiator, water often needs topping up to restore pressure.
- A small leak in the system — a fitting, valve or radiator leaking slowly, invisible from day to day.
- Faulty expansion vessel — if it no longer does its job, pressure drops faster than normal.
- Filling valve left open, or conversely never used again after a long period.
What you can safely check yourself
Check the exact pressure
The gauge should read between 1 and 2 bar when cold. Below 1 bar, topping up is needed.
Top up if you know how
If your installer has already shown you the filling valve, open it gently to around 1.5 bar, then close it again.
Pressure drops again quickly? Call a professional
Repeated pressure loss points to a leak in the system — it needs to be located by a licensed technician.
Which brands does this code apply to?
This code is used as-is on Vaillant and Bulex boilers, two brands that share the same technical platform. On Junkers, Viessmann, Atlantic and Remeha boilers, an equivalent fault shows under a different code — our technician identifies the fault on site, whatever the brand.
A clear price, no surprises
A fixed 35 € call-out fee in Brussels, Wallonia and Flanders. The repair price is given to you before any work starts. Free, no-obligation quote on 0488 02 77 07.