Union fittings allow two pipes to be connected in a manner that can be quickly disassembled for maintenance or replacement. Two sides of the pipe are set into union fittings, which are then joined together to finish the connection. Unlike copper pipes, which require soldering, galvanized steel pipe is connected using pipe threads that screw into each other. This makes connecting a galvanized union fast and relatively straightforward. Once installed, a galvanized union connection can be removed using two wrenches and elbow grease.
Things You'll Need
Liquid pipe dope
Galvanized steel union fitting
Place a 1/4-inch bead of liquid pipe dope around the center of the pipe threads on one side of a galvanized steel pipe.
Place the end of the pipe into the top of the galvanized steel union fitting and turn the fitting clockwise until tight.
Place a pipe wrench around the fitting and turn it clockwise until very tight.
Place a 1/4-inch bead of liquid pipe dope around the center of the pipe threads on the pipe that you want to join with.
Place the end of the pipe into the bottom of the galvanized steel union fitting and turn the fitting clockwise until tight. Finish tightening the connection with the pipe wrench.
Remove the connection for maintenance or repair by placing a pipe wrench around the center of the union fitting, not the nuts around the pipes, and turning the fitting counterclockwise. The pipes will pull apart but still have one half of the union on either side for quick re-assembly.
Dielectric unions can also be used to connect galvanized steel to copper pipes. These unions contain a non-conductive barrier that separates the copper from the steel, but holds together the same way.
Only use galvanized steel fittings with galvanized steel pipes as mixing materials may cause a slight electrical current that will corrode your plumbing system over time.