Civil 3D - Issue: Pipe Length (Center vs Walls)

September 21, 2021 Leo Lavayen

When labeling Civil 3D Pipe lengths have options for Center to Center or Inside Walls. 

When the pipe is connected to the center of structure (the Civil 3D default), the 2D Length – Center to Center label values works as expected.



If the design is Center-to-Center but the label option for Length To Inside Edges is used the displayed label is incorrect.  Autodesk is aware of this issue and it has been sent to their development team (CIVIL-40352 ).   The releases of Civil 3D 2019 - 2022 the math driving the label is incorrect.  This label worked in the 2018 release of Civil 3D.

To track the issue, labels decimal places have been set to 4, and the design made simple to calculate the 2D distances.  The Pipe from Center-to-Center measures 100.0000’ and the connected structures on both ends are and even 4’ inside diameter, the resulting length to inside diameter should be 96.0000’.  However, label is showing a value of 96.3682’.

Spent about a day troubleshooting before sending it to the Autodesk support team and finding out it was a “known” issue.   As shown below, the correct values to inside walls (96') is displayed when the pipe slope is set to 0.00%.  Somehow pipe slopes are playing a factor in math. 



The design will be altered using a a function added to Civil 3D a few years back to Pipe Rules: Set Pipe End Location

When the rule for End Location is set to Structure Inner Wall, it causes the the physical pipe ends to be shifted to the inside wall of the connected structures, instead of the default center.  Notice if we are to HOLD starting pipe invert elevation (80.00) and the grade (10.00%), the end invert is adjusted (70.40) due to a shorter pipe. 

The “fix” for the label is interesting, as the previously used 2D Length – Center to Center (top label) option IS the label style configuration we want to use.  Notice, here that again the label option for 2D Length to Inside Wall is still incorrect.



To show inside wall lengths, leverage Pipe Rules to Set Pipe End Locations, and a single label style to accurately display lengths of pipes when connected to the Center or to Walls of structures.  Hopefully, Autodesk will correct the errors in the Civil 3D labels in a future release.

About the Author

Leo Lavayen

Civil Applications Expert<br><br>As an Applications Expert, Leo is responsible for supporting, training and implementation of software for survey and civil engineering professionals. He has more than 17 years of experience helping large and small, public and private clients in the eastern United States.

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