I have installed a radiator in the loft which is the same level, if not then slightly above the header tank. For the heating to work i must switch it on, so that the pump will pump water to this radiator. But i must bleed it too before it works. When i switch it off then the loft rad drains and i have to repeat the process again. The header tank overflows too. Do i need to fit the header tank above the rad, or is there another way ? It is not a combi boiler, but the old style.