BoilerFaultCodesVaillant F22 Fault Code
The Vaillant F22 fault code means: your boiler has stopped working because the water pressure is too low for it to operate safely.. It appears on 6 Vaillant models in our database.
Technical description: Fault F22 will be stored in the fault list if the water pressure falls below 0.03 MPa (0.3 bar).
What causes the Vaillant F22 fault?
This fault occurs when the water level inside your central heating system drops too low for the boiler to function safely. The most common reason is a slow leak from a radiator valve or a pipe joint, but it can also happen if you have recently bled your radiators without topping the water back up.
This fault is frequent in autumn when homeowners turn their heating back on for the first time and discover pressure has dropped over the summer months.
DIY fix possible
Locate the filling loop handles (usually two blue or black taps) underneath the boiler.Slowly turn both handles 90 degrees to allow water into the system while watching the pressure gauge.Close both handles fully once the pressure reaches between 1.0 and 1.5 bar.
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Vaillant models that show the F22 fault code
Click a model for the full fault code list and model-specific repair notes.
Source
Vaillant F22 fault code information on this page is sourced and cross-checked against the official Vaillant service / installation manuals for each affected model.
- Vaillant ecoMAX 824E manual (PDF)
- Vaillant ecoMAX 828E manual (PDF)
- Vaillant Home Combi 35 manual (PDF)
Reviewed by the BoilerFaultCodes Editorial Team · Last reviewed 31 August 2026