Couplings are A further popular choice for connecting galvanized pipe without the need of threads. They are available in a variety of styles, such as slip couplings, force-in shape couplings, and compression couplings. The installation process differs a little bit dependant upon the type of coupling utilised, but commonly involves: https://www.malleableiron-pipefitting.com/industry-knowledge/how-to-connect-non-threaded-galvanized-pipes.html