A method of forming a tube joint which can be used in a desalination plant includes providing a fluted tube (1), applying a sealant (51) to the tube end (19) and inserting the tube end (19) into a tube sheet or plate (3) to form a joint therebetween. After insertion, the inner surface of the fluted tube (1) is worked to deform external ridges of the fluted tube (1) and uniformly distribute the sealant (51) throughout the joint area. The fluted tube (1) is deformed using a roll expanding method. The fluted design of the tube (1) retains sealant (51) in the joint area during tube (1) insertion and expansion and takes advantage of the heat transfer characteristic of the flutes (9) to provide an improved joint construction especially adapted for heat exchange use.