There has been numerous instances where I have desired to use a pipe as a "generic holder of information" and then have it add up.
Such as:
Steam (Lbs/Hr)
Condensate (Lbs/Hr)
Med Gases (Number of Outlets)
Compressed Air (CFH)
Natural Gas (CFH)
Physical Electrical Conduit Runs (KW)
I end up using the pipe and make the GPM value a numerical place holder. Even though it is in my mind Lbs/Hr or outlets of med gas or whatever. This is sort of lame, but does work okay.
What I am saying: Make there be a "generic pipe", that parameters can be added to with our own units. Or have it be unitless, and just have a "cell" for flow and other useful data to pass along.