i have a little red knob under my boiler i am sure this is the prv??? it seems to be loose i have no pressure in my boiler and have tried to top the system back up but this still stays on 0 any advise ??

keannan, November 2012

hi dont touch that red thing. its a prv it opens when the boiler has been filed to much leting the water out tampering can cause it leak constantly. anyway the valve you are looking for is 2 grey knobs more near the front underneath u need to turn them both on to fill the boiler. download the vaillant pdf user instruction online it will show the valve. if this helps it should have like a silver flexi pipe linking the 2 knobs to identify it

kash, November 2012