Slightly confused....2 tanks in loft, only bother with the small one. It will have a cold water inlet at the top, a flow and expansion pipe at the bottom, and an expansion pipe that curves over the top. This tank should have around 4" of water in it, and when you drain or bleed the rads the water should be replenished. So, if the tank has water in it, either the rad valves are off or they are blocked with sludge. If the water that bleeds out is black, then its likely to be a sludge blockage issue.
John, October 2009
