The usage of direct plumbing components in more mature galvanized pipe units, which can develop a possibility of direct contamination. Compression fittings give you a quick and practical solution for connecting galvanized pipe with no threads. They consist of a human body, nut, and ferrule. To work with compression fittings: https://www.malleableiron-pipefitting.com/industry-knowledge/how-to-connect-non-threaded-galvanized-pipes.html