You need to turn off both valves at either end of the radiator, depending on the type of valves you have this procedure differs thermistatic valves just tern them to 0 or if you have normal valves using a screwdriver remove the tops then turn the spindle clockwise. You now need an adjustable spanner or some water pump pliers and a couple of containers to catch the water. Simply loosen the back nut at one end of the radiator and allow it to drain there may be a little pressure initially but once its started to drain off it goes. Hope this helps.
andisugg, January 2010
