1/2" Copper Test Cap. Hard Copper Pipe is generally used for 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 application. Solder fittings require clean, and lubricated connection surfaces, along with heat to create the best and longest lasting connection. This This 1/2" Copper Test Cap is designed for water and air testing your copper line.