Abstract: A method for replacing tubes in a drum or header without removing the whole tube entirely is disclosed. According to the method, the old tube is cut off level with the header-member; a recess coterminous with the diameter of the tube is machined into the header creating a seat for a new tube; the recessed old tube end is beveled and the old tube is welded into the header-member along the bevel; and a new tube is inserted into the seat and welded to the exterior of the header-member. In a preferred embodiment, a countersink is machined in the surface of the header-member to create a greater surface for welding of the new tube.