I've got a radiator that won't heat up, bled it, and the others, balancing has been fine up until now, all other rads get hot. Not ideal with a cold snap incoming. Problematic one takes ages to heat up, and tends to stay lukewarm at the bottom, i believe this indicates sludge in the rad, so I'll get it off and hose it down once I get someone round to give me a hand as won't be able to lift it off by myself. Not got a problem with doing this (assuming I can get the thing back on afterwards!) However adding inhibitor back into the system with a magnaclean filter I'm yet to do, my plumber showed me how when he first installed the boiler (which has been served every year since install), of which the only real thing I can remember was, pour it into the magnaclean filter and job done! Can't find any decent youtube vids of this process, they are all shit, so may end up doing one myself but is the instructions below (lifted from Adding inhibitor in magnaclean filter. - MoneySavingExpert.com Forums) pretty much right? Can I actually leave the system on, once it's done, or is it recommended to turn the system back off after 30 mins?