We may have found other answers which could help you.
Click here for Vaillant Pressure DropVaillant condensing boiler ecoTEC plus?
Vaillant eco plus 531 boiler?
how to fix water pressure its down at bottom of grey part?
Vaillant VCW-Sine18 T3WFH Lights but then goes off after 5 Min?
What does f.25 mean?
vaillant ecoTEC plus boiler fault code - how to fix?