BoilerFaultCodesVaillant F.22 Fault Code
Also written as F22 — same fault.
The Vaillant F.22 fault code means: your boiler has detected that there is not enough water pressure in the system to operate safely, causing it to shut down to prevent overheating.. It appears on 50 Vaillant models in our database.
Technical description: Dry fire protection | No water in appliance, pump cable defective, pump blocked or defective, pump output too low
What causes the Vaillant F.22 fault?
This fault occurs when the boiler's internal sensor detects that the system pressure has dropped too low for the unit to heat water safely. The most common reason is a slow leak somewhere in your radiator network or a faulty expansion vessel that can no longer regulate pressure correctly. Without enough water to circulate, the boiler shuts down to prevent the heat exchanger from overheating or sustaining permanent damage.
This fault is more common in autumn and winter when the heating is first turned on, as the increased pressure of hot water can expose small leaks or reveal that the system lost pressure while sitting idle during the summer.
DIY fix possible
Locate the silver braided filling loop hoses underneath or near the boiler.Open the two small valves on the filling loop to allow water into the system.Watch the pressure gauge on the front of the boiler until it reaches between 1.0 and 1.5 bar, then close both valves tightly.
Find a Gas Safe engineer
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Vaillant models that show the F.22 fault code
Click a model for the full fault code list and model-specific repair notes.
- ecoFIT Pure 412 Repair: £0-120
- ecoFIT Pure 418 Repair: £80-150
- ecoFIT Pure 425 Repair: £80-150
- ecoFIT Pure 435
- ecoFIT pure 612 Repair: £80-150
- ecoFIT pure 615 Repair: £80-150
- ecoFIT pure 618 Repair: £80-150
- ecoFIT pure 630 Repair: £80-150
- ecoFIT Pure 825 Repair: £80-150
- ecoFIT Pure 830 Repair: £60-120
- ecoFIT Pure 835 Repair: £80-150
- ecoFIT sustain 415
- ecoFIT sustain 418
- ecoFIT sustain 430
- ecoFIT sustain 615
- ecoFIT sustain 618
- ecoFIT sustain 630
- ecoFIT sustain 825
- ecoFIT sustain 830
- ecoFIT sustain 835
- ecoMAX Repair: £0-180
- ecoMAX 613 Repair: £0-280
- ecoMAX 618 Repair: £0-280
- ecoMAX 622 Repair: £0-280
- ecoMAX 635 Repair: £0-280
- ecoMAX 824/2 E Repair: £0-280
- ecoMAX 828/2 E Repair: £0-280
- ecoMAX 835 E Repair: £0-280
- Ecomax Condensing 600/800 series Repair: £80-120
- ecoTEC exclusive Repair: £0-120
- ecoTEC plus Repair: £0-120
- ecoTEC plus VU GB 656/4-5 A Repair: £80-150
- ecoTEC pro Repair: £0-160
- ecoTEC sustain Repair: £0-120
- Home Combi 25 Repair: £80-150
- Home Combi 30 Repair: £80-150
- Home Combi 35 Repair: £80-150
- Turbomax 824/828 Repair: £120-250
- Turbomax Plus Repair: £120-250
- Turbomax Plus Repair: £80-120
- Turbomax Plus 824/828E Repair: £0-180
- Turbomax Plus 824/828E Repair: £80-120
- Turbomax Plus 828 Repair: £120-350
- Turbomax Plus 828 Repair: £0-120
- Turbomax Plus 828 E Repair: £0-180
- Turbomax Plus 828 E Repair: £80-120
- Turbomax Plus VUW 242E Repair: £0-180
- Turbomax Plus VUW 242E Repair: £80-120
- Turbomax Plus VUW 242EH Repair: £0-180
- Turbomax Plus VUW 242EH Repair: £80-120
Source
Vaillant F.22 fault code information on this page is sourced and cross-checked against the official Vaillant service / installation manuals for each affected model.
- Vaillant ecoFIT Pure 425 manual (PDF)
- Vaillant ecoFIT Pure 435 manual (PDF)
- Vaillant ecoFIT pure 630 manual (PDF)
Reviewed by the BoilerFaultCodes Editorial Team · Last reviewed 31 August 2026