What term describes the length of a pipeline measured along the centerline of the pipe or fitting?

The term that describes the length of a pipeline measured along the centerline of the pipe or fitting is known as "developed length." This measurement is important in plumbing and piping design because it helps to accurately determine the overall length of piping that will be required for installation. The developed length accounts for the bends, fittings, and other elements in the piping system by measuring along the centerline, providing a more accurate representation of the material and length needed compared to other methods of measurement.

Other options like actual length, measured length, and effective length do not capture this specific definition as accurately. Actual length typically refers to the physical measurement taken directly from pipe to pipe without considering the layout, while measured length might vary based on how the lengths are accounted for in relation to installations. Effective length can pertain to factors that impact fluid flow and pressure, but it does not specifically denote the centerline measurement of the piping. Thus, developed length is the precise terminology used in the plumbing industry for this purpose.