first you will need to drain system completely down, on one side of rad there is a valve that is tamperproof,this is used to balance rads,on other side of rad remove valve and undo nipple screwed into rad(usually 1/2 " bsp)new valve will have new nipple,use ptfe tape on thread and tighten (you may need a special tool to remove/refit nipple,looks like a big allen key)tighten all connections and refill system from furthest rad to nearest(from boiler)
steeveepee, October 2008
