A pipe coupling assembling for use with a pipe having an inner wall, an outer wall and an interstitial space between the walls, with the pipe terminating in a coupling end defining an axial direction. The assembly includes a ferrule attached to the outer wall. The ferrule has an outer annular ring and an interstitial channel aligned with the interstitial space in the pipe for presenting an interstitial chamber. An insert is attached to the inner wall. The insert also has an inner annular ring. An externally threaded transition fitting is removed for attachment to the ferrule. The fitting includes an interstitial channel aligned with the interstitial chamber, an outer seal channel for sealing engagement with the outer annular ring, and an inner seal channel for sealing engagement with the inner annular ring. Finally, a coupling is keyed to the ferrule including internal threads for engagement with the fitting to provide coupling engagement between both the ferrule and the insert with the fitting.