I felt a need to weigh in here, even though the post is getting a little old.
The original question was can piping from one floor be re-routed to a lower floor, then returned to the original (first) floor (without adding branches, outlets, or other on the lower floor).
The discussion turned to service valves (an all-important, and often overlooked valve, IMO.)
Here is my take on the original question:
If you have a procedure room (Cath Lab) with outlets in a pedestal (stainless steel box on floor), you run piping from your zone valve down the wall to the ceiling space of the floor below you, then penetrate the floor where the pedestal is to be located.
What is the difference?
In both cases the piping will be routed at some point to another floor, after being fed from a valve that is only to serve a room or rooms on the same story.
I understand Luke's interpretation of Branch lines. But for me, key words are "serve a room or group of rooms on the same story". I believe they are, even if the pipeline drops down a floor for a bit...
One concern is to somehow assure that this line is never altered (in the future) to feed more than one floor. I believe additional labeling should be required.
