Huy Guys, Heeeeeeelp!!! I have one of these; and one of these; to dose the sealed central heating unit. I have emptied the entire system of water.... I then attach the bottle to the dosing kit and screw it onto the filling loop. I then open the valve and it will NOT go in. Aaaargh!! I've squeeze the bottle so hard it nearly burst but the liquid will not pass into the boiler?!?! What am I doing wrong? I can't see anywhere else in the system where I can add the chemicals. I don't understand why it won't go in. If I fill the system with water it goes in fine.