how can i stop my c/heating header tank from dripping?

problem solved, thanks to all who replied.BP

Brian
February 2010

Replace the washer as in other answer & make sure when you have finished the water level is well below the overflow pipe outlet as water expands when heated & this will raise the water level in the tank causing it to overflow, you only need about 2-3 inches of water in a central heating header tank,

bamba
October 2009

rubber washer inside the ball cock arm, needs changing/replacing

wirecutterman
October 2009