The NEC has "forever" required that pipe be supported within 18" of its' termination. This seems simple enough, but some folks will try to debate the meaning of "is."
That termination is itself a support seems self-evident. That you need space for your box offset, etc., also seems obvious. Finally, that you might want to mount to wall framing- and such framing is typically on 16" centers- seems reasonable.
The debate begins when you start to make inferences from that rule.
The first issue for Wormtongue is "termination." Does the pip 'terminate' at it's end? Would not every coupling then require a support? To make such an inference would require that every stick of pipe required two supports. Since pipe typically comes in 10-ft., lengths, there would be no need for that other code rule requiring supports not be more that 10-ft. apart.
(Remember now that part of Article 90 that says the code is not an instruction book, and pre-supposes that you already know the trade?) Alas, we're getting more and more 'experts' and 'authorities' who never pulled a wire or bent a pipe.
The next inference was: if I'm going from box to box, and the boxes are less than 36" apart ... then every point of that pipe is within 18" of a termination .... so I don't need a support. That's the inference that this code change attempts to address. I'm not sure it has - or if it has only confused things further.
IF I were to go by past experience, I would guess that the panel was trying to enshrine the existing trade practices.
What they really need to do is to find a way to exclude codebook commandos from the mix.
BTW ... not addressed anywhere in the code is the effect a change in direction has on support. That is to say that after you change direction 90 degrees, you have exactly zero support left. Ever see a shower where the shower rod was bent around a corner? It's pretty basic math. I'll bet those who went through an apprenticeship were taught some manner of 'rule' about this- but it's not in the book.
I've already seen one person distribute pictures of two cabinets 24" apart with unsupported conduit, asserting 'violation!' My take is: if that's the worst thing you can find, it's a pretty good install!
Oddly enough, I have something in my shop where the 'pipes' are supported within 18" of their terminations.' I call it a ladder.
