While you wait for answers, we may have found some information which could help you.
Click here for Vaillant Gb 221Vaillant condensing boiler ecoTEC plus?
Vaillant F22 fault?
how to fix water pressure its down at bottom of grey part?
how do I rectify the fault as detailed below?
Vaillant eco plus 531 boiler?
Vaillant 828E - no hot water?