ICE said:
We need to get to the bottom on this one. If what you say is correct, I have a been getting it wrong for years.
NOTE TO ALL THIS QUOTE IS FOR THOSE UNDER THE UPC NOT IPC
CPC 1211.3 Concealed Piping in Buildings.
1211.3.1 General. Gas piping in concealed locations shall be installed in accordance with this section. [NFPA
54:7.3.1]
1211.3.2 Connections. Where gas piping is to be concealed, unions, tubing fittings,
right and left couplings, bushings, swing joints, and compression couplings made by combinations of fittings
shall not be used. Connections shall be of the following type:
(1) Pipe fittings such as elbows, tees, and couplings.
(2) Joining tubing by brazing (See Section 1209.5.8.2).
(3) Fittings listed for use in concealed spaces that have been demonstrated to sustain, without leakage, any forces due to temperature expansion or contraction, vibration, or fatigue based on their geographic location, application, or operation.
(4) Where necessary to insert fittings in gas pipe that has been installed in a concealed location, the pipe shall be reconnected by welding, flanges, or the use of a ground joint union with the nut center-punched to prevent loosening by vibration. [NFPA 54:7.3.2]