Hi, My heating system was changed from a vented to unvented OIL system. I have a magnaclean, nearly all the radiators are new. The maganclean is cleanish after months of use. I keep getting air in my system, and before you chastise me, I swear I cannot see any leak. The pressure keeps dropping too, until it gets to about 0.3 bar and then stays there. The tallest radiator is four floors up from the heating pump. The hot tank is on the third floor where the pipes from the boiler go first and then to the second floor to the manifold. The pipes are micro pipes to the radiators from the manifold, but I think 3/4 inch from the boiler to the manifold. I am grateful for any advice given including what kind of heating pump I need to pump up 4 floors. Thank you.