I agree with Dan. I don't think you can label this sort of connected-to-a-structure pipe separately, just within in the structure label itself. And even then, there are limitations. About the best you can do is have the structure label call out the pipe size, invert elevation, and IN or OUT flow direction. (There are many other parameters that can be called out, of course, but the point is they are all within the structure label, not a separate pipe label.)