Abstract: The plumbing assembly includes a tube having a free edge portion at which at least one inverted T-shaped projection is formed. The projection is located with its cross bar extending parallel to the free edge of the tube and the stem thereof extending from the cross bar towards the free edge and terminating at a point spaced therefrom. An annular ring formed with a threaded outer peripheral surface and a relatively smooth inner surface has at least one recess formed in its inner surface for receiving the stem portion of the T-shaped projection, thereby to prevent relative rotation between the tube and the ring.