Joining Black Iron Pipe

Black iron pipe, most commonly used for gas piping, comes in 3/8 inch, ½ inch, and ¾ inch diameters. Larger sizes are available but not commonly found at hardware stores and home centers.

Black pipe is available pre-threaded, with male threads at both ends, in various lengths. The pipe is joined using a variety of female threaded couplings. Straight couplings and tee fittings are available, as are 45-degree and 90-degree elbows.

Black pipe is used to carry natural gas.
  1. Apply Teflon tape to the pipe threads of both pieces to be joined, by wrapping the threads three or four times. You can also use pipe joint compound (also known as pipe dope). Pipe dope is a thick paste, and is applied to the pipe threads with a brush.
  2. Thread the coupling or elbow onto one of the pipes by hand, then tighten one full turn using the pipe wrenches.
  3. Thread the second pipe into the free end of the fitting attached in step two. Again, tighten the pipe finger tight plus one turn with the wrench.
  4. Check for leaks.

Things You Will Need

  • Black iron pipe
  • Pipe fittings
  • Teflon tape or pipe dope
  • Pipe wrenches


  • Be careful not to over-tighten the fittings; over-tightening can cause fittings to crack or split.
  • If you can't turn an existing pipe to screw it into a coupling or elbow, use a union to join two pipes.


  • Don't use black iron pipe for water.

About the Author

David Brown began his writing career while still in college, writing and editing research grants and scientific papers. His work has appeared in such journals as "The Journal of Clinical Investigation" and "Gastroenterology." He currently owns a construction company in Boulder, Colo.

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