Use of left/right nipple and coupling

Hello,
I'm looking for some guidance on the proper use of a left/right nipple and coupling to join two rigid pipe assemblies. As I understand it, the left-handed end of the L/R nipple and the threaded end of the other pipe assembly should be in line with just a small gap between them, maybe 1/4" for 3/4" iron pipe? Then you have pry them apart to insert the L/R coupling, and tightening the coupling draws the two threaded ends together. Do I have this right? It seems like the two assemblies must have some give in them in order to be able to insert the L/R coupling.
Thanks, Wayne
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I am a little lost by your description. If you have two runs of thread pipe that you are trying to join, I would use a union.
What is the material? What is the project? I think any of us would need this information to help. ______________________________ Keep the whole world singing . . . . DanG (remove the sevens) snipped-for-privacy@7cox.net

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I'm doing gas piping, and unions are only allowed in exposed locations. So I need to use a left/right nipple and coupling, per the inspector.
Thanks, Wayne
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Not sure if I posted this already, but the inspector told me to use a left/right coupling. I'm working on natural gas piping, so the use of unions is limited.
Thanks, Wayne
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Your description and assessment sound correct. As the other poster said, a union would be the alternative method for joining two iron pipes together. Just be sure to get the same metal (don't mix black pipe with galvinized pipe even though they will fit).
I prefer a union because they can be opened and both ends tightened independently if you have a leak. The nuts also are bigger making it easier to hold onto with a couple of wrenches. THe pipes get pushed (in line) less with a union also. If the pipes can be pushed out of line (as is usually easier) this also aids in the installation of the union. Its only drawback is that it has three gaps to leak instead of 2 and it is a little fatter.
Usually I have a bag of nipples from close to 5" (in 1/2" increments) so I can get the union right where I need it.
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