So, I have a towel rail which is cold at the top and hot at the bottom. I thought that I would follow internet instructions and bleed it. This however, has drained the pressure from the system. So, I went to increase the pressure and the turnkey which should be in the tray underneath is nowhere to be found. I am pretty sure that this is an unvented system - we have a megaflow, if that has anything to do with it. My question is this - am I going to do any damage to my system by still running the heating and hot water? Also, the bleed valve was positioned upside down on the rail (helpful design, I know). I hope but am not certain that it is completely shut. Would I know if it was not?