A heat exchange assembly adapted for use in a water tank is provided. The heat exchange assembly includes a tube having end portions and a coiled portion between the end portions. A fitting is connected to at least one of the end portions of the tube. The fitting has an end configured to extend through an opening in the water tank, and a surface positioned to limit the extension of the end through the opening in the water tank. The fitting also has an opposite end defining a bore configured to receive one of the end portions of the tube and to limit the extension of the end portion of the tube into the opposite end of the fitting. The bore extends axially beyond the surface of the fitting.