Besides choosing the right couplings, There are several additional things to consider you’ll must note and proper prior to connecting the pipes. In this article’s what you must check: To connect threaded galvanized pipe, include many of the threads with pipe dope, or wrap the threads with PTFE plumber's tape. https://www.malleableiron-pipefitting.com/industry-knowledge/how-to-connect-non-threaded-galvanized-pipes.html