Black pipe and galvanized pipe are the same material with just one difference: galvanized pipe is coated with zinc to prevent the underlying steel from corroding. Galvanized piping was commonly used in pipes that carried drinking water--before the widespread use of copper piping and PEX tubing. Black pipe was used in drain lines, heating piping and natural gas piping. Black pipe can be used in lieu of galvanized pipe as long as the piping system isn't for drinking water. Since both pipes are basically the same material, they fit together with ease.
Things You'll Need
Take a wire brush and brush the threads of the black pipe thoroughly to remove any corrosion and rust. Apply a little penetrating oil to the threads if you won't be using the pipe immediately. Water or humidity can cause rust to reform rapidly.
Wrap the threads of the black pipe with teflon tape. Apply the tape around the threads until it is a thickness of two to three layers of tape. The tape should wrap around clockwise if you are looking at the end of the pipe.
Screw the black pipe into the galvanized pipe until it is hand tight. Place a pipe wrench on the black pipe and turn the pipe clockwise until tight.
Connect any other piping together in the same manner.
Black pipe is less expensive than galvanized pipe because it lacks the zinc coating. If galvanized pipe isn't required for your system, stick with the black pipe to save money.