SUDA Tip: Best Practice for Creating Pipes Between Nodes

Written by: Robert Garrett

I often get the question: Does it matter which direction I create pipes for my drainage or sanitary networks?

The simplest answer is: It only matters when connecting to a head wall.

The best practice answer is: Always create the pipe in down stream direction, if you know the direction.

In the image below, the arrows indicate direction of flow and the direction that the pipes where created.

SUDA-Pipe Direction 1

Always create pipes in direction of flow, if you know it.

Here’s the reason for the recommended best practice:

  • When connecting to a head wall, the software will automatically define the boundary condition of the head wall as an inlet or as an outfall based on whether the head wall is the beginning or ending node.
    • If the pipe ends at a head wall then the head wall is defined as an outfall.
    • If the pipe starts at a head wall then the head wall is assigned as an inlet.

SUDA-Pipe Direction 2 SUDA-Pipe Direction 3

  • Once the head wall boundary condition is assigned, it can only be changed by reversing the direction of the pipe.
  • Also, taking a look at the property panel for the pipe, some of the properties are labeled as “Start” or “Stop”, as seen below.
  • By adopting a standard practice of creating pipes in the downstream direction then:
    • Head walls are always assigned correct boundary condition.
    • In pipe properties, “Start” always means upstream and “Stop” always means downstream

SUDA-Pipe Direction 4


Robert Garrett

Robert has over 25 years experience as a practicing engineer and is licensed in the State of Tennessee. After graduating from Tennessee Technological University, Robert worked for the Mississippi State Highway Department, Bridge Design Division. Then he spent 12 years with the Tennessee Department of Transportation in the Roadway Design Office and later served as Regional Manager in the Design Survey Office.From 2000 to 2006, Robert worked for Robert G Campbell and Associates in Knoxville, TN where responsibilities included roadway, site, and utilities design projects.Joining Bentley Systems in March 2006, Robert wrote specifications & documentation for software development. Duties included testing, customer feedback and ensuring the products met the needs of the civil engineering user base. He also developed training material for education both internally to Bentley and for outside organizations. He served as Product Manager for Utilities Products, including the new OpenRoads Subsurface Utilities Design and Analysis software. Robert also provided guidance and implementation services for new technologies.He is a frequent presenter and trainer at user conferences.

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