The dimension lines that display in the sketch are interactive. You can use the dimension lines that display in the sketch to modify the dimension of any section of the pipe route.
Select Show Automatic Dimension Lines 
on the Tools toolbar to toggle on and off the display of dimension lines.
-
Right-click the dimension line for the length of pipe to modify.
The software displays the Dimension box with the current length highlighted.
-
Type the new length directly into the Dimension box, and then press ENTER.