the one with the black control handle.located on a chrome flexible pipe below boiler.second from right pipe beneath
boiler.
diy expert,heating engineer, December 2012
here is a pic of the part u will looking for its called a filing loop just turn the valves as you see them and u should see the pressure rise. just copy this website link.
http://www.screwfix.com/p/r24-filling-loop/83905?kpid=83905?cm_mmc=Google-_-Product%20Listing%20Ads-_-Sales%20Tracking-_-sales%20tracking%20url&gclid=CMeCn-GXorQCFaTKtAodkWgA4w
