The Correct Installation of a Stainless Steel Pipe Union

Gas and stainless steel pipes come in many lengths and with threads at both ends. In general, union joints are installed into pipelines so that the pieces of the pipe in the middle of the line can be removed if needed. Installing the union is not that hard to install, as long you have the right tools and steps. Here are the guides on how to do it.

Things you need

  1. Pipe
  2. Pen
  3. Measuring Device
  4. Cutter Blade
  5. Cutting Oil
  6. Wrench

Stainless Steel


  • Shut off the water or gas system to prevent any running energy source through the pipe where you will be installing the union.
  • Use a felt-tip pen to mark the steel pipe at the point where the unions need to be installed.
  • When all the three parts are installed together, measure the length of the union.
  • From this figure, subtract the amount that the steel pipe’s threads will need to enter both ends of the union.
  • Make a second mark along the pipe at a distance from the first mark that equals to the calculated measurement.
  • Place a rotary pipe cutter around the pipe and tighten the cutter blade onto one of the marks.
  • Lubricate the cutter blade and the pipe with cutting oil. Rotate the cutter 360 degrees once and then tighten it again. Rotate it again. Repeat this process until the pipe is cut off.
  • Proceed with the same steps at the second mark.
  • Remove the pipes on each side of the cuts by placing a pipe wrench around the pipes at a point close to the nearest couplings.
  • Remove the pipes by turning the pipe wrench counterclockwise. Bring the pipes to the hardware store to have the cut pipe ends threaded.
  • Apply a threading compound around the older threads on both pipes, threading both pipes by hand into the couplings that they were removed from. Tighten the pipes with a wrench.
  • Apply a threading compound to both newly threaded pipe ends. Remove the female end of the union from the male end as the female end will have the central nut.
  • Thread the female end of the union onto one of the pipe threads. Tighten it in place with the wrench.
  • Thread the male end of the union onto the remaining pipe end and then tighten it. Thread the central nut onto the male end of the union by hand.
  • Tighten both together with one wrench on the central nut and another on the male end.

Image Credit:

Flickr CC

Additional Reading:

Steel Ships and Iron Pipe