While there is no way to label the total length of pipes in a NETWORK, it is very easy to get the total lengths in a RUN of pipes in plan and/or profile. Just select the Spanning Pipes Plan or Spanning Pipes Profile label-type and use any label that has a pipe length characteristic in it. When prompted to select pipes, pick the first pipe in the run, then the last pipe in the run, hit ENTER, and select the pipe that you want the label attached to. The label will automatically add the lengths of pipes and place them in the label text. Additionally, you can add to the label the Number of Pipes in Span to help clarify, if you want.
An important part of this particular labeling sequence is, upon completion, to stand up and announce in a clear voice, "Man, I'm good!!" Advanced C3D users can follow that up with the sound of a frosty one being popped, followed by three "glug" sounds and a contended "Ahhh..."