This Copper 2" Copper Union Sweat x MIP is designed to connect two different form of pipe lines. This Union features a copper inlet and a galvanized pipe inlet also. The union reduces vibration and corrosion between the two pipes. Copper 2" Copper Union Sweat x MIP. Hard Copper Pipe is generally used for the supply of hot and cold water in both commercial and residential applications. Rigid or hard copper is always soldered, crimped, or pressed as the form of connection. Copper offers a high level of resistance to corrosion and needs fittings to get around bends and obstacles. Copper fittings also range in the application. Solder fittings require clean, and lubricated connection surfaces, along with heat to create the best and longest lasting connection.