A joint assembly, including a piping, comprises a joint end sleeve, a tightening ring and a nut. The ring has an external truncated-cone shaped surface and an internal cylindrical surface with a diameter slightly larger than the diameter of the piping, and an internal cylindrical surface with at least one annular edge to cooperate with at least one annular groove in the sleeve in such a way that an inside diameter of the annular edge is substantially equal to the outside diameter of the piping. The nut has an internal cylindrical surface with a diameter slightly larger than the outside diameter of the piping and is disposed opposite a cylindrical portion of the sleeve when the nut is installed. The smaller outside diameter end of the tightening ring is adjacent the internal cylindrical surface of the nut when the nut is installed. An internal truncated-cone shaped surface of the nut has a larger diameter end a size slightly larger than a smaller outside diameter end of the ring.