The article presents the results concerning the repair welding of a long-operated waterwall using the mechanized TIG method. The tests were focused on determining the effect of a repair performed in order to remove cracks in welded joints located along flat bars opening on the tube wall side on the structure and hardness of the heat affected zone (HAZ) of a repair welded joint in the waterwall. In addition, the tests investigated the influence of multiple repair welding on the formation of structural notches in the HAZ.