i've made up something to put inhibitor into sealed systems, get a McA washine machine spigot cut off the spigot where the 3/4"BSP thread starts, screw on a 3/4" FI x 15mm tap adaptor a little bit of Hep2O pipe with a hep bend on it then a bit of pipe fitted to a 15mm st coupling, remove the bleed valve from a rad screw the st coupling into the rad (it spins on the hep bend) and fill from the wash mac spigot as it acts as a small funnel, takes 15mins to make it but then you have it for other jobs