Modeling non-standard conduit or channel shapes

Product(s): SewerGEMS, SewerCAD, StormCAD
Version(s): V8i, CONNECT Edition
Area: Layout and Input


How can I model a conduit or channel that has a non-standard shape, such as an arch, ellipse, or a rectangular-bottom with tapered sides?

Or for example the shape that you want to model does not exactly conform to the definition of the shape as defined in the Help documentation.


Both the conduit and the channel element can be used to model non-standard shapes. For a conduit, the shape is defined in the conduit itself (and is always treated as prismatic) and for a channel, the cross section is defined at the cross section node elements, at the ends of the channel link elements. For more on the differences, see: Conduit vs. Channel

When assigning conduit or cross section shapes, you have two options: user defined or catalog. The catalog conduit library for example consists of standard conduit shapes, sizes and materials. To assign a non-standard shape (a shape not readily available in the conduit library), the user can create different conduit shapes and use them.

The following steps outline how to create a non-standard, catalog conduit or cross section shape that can be shared for future projects. You can also define non-standard shapes when your conduit or cross section type is set to User Defined.


Go to Components>Catalog>Conduit Catalog (or for older versions such as V8i, Components>Conduit Catalog)

Step 2

In the Conduit Catalog click on new to create new user defined shape.

Click on Conduit Shape to select a shape to be assigned. Allowable conduit shapes include;

  • Basket Handle
  • Box
  • Catenary
  • Circle
  • Egg
  • Ellipse
  • Gothic
  • Horseshoe
  • Irregular Channel
  • Irregular Closed Channel
  • Modified Basket Handle
  • Parabolic Channel
  • Pipe Arch
  • Power Channel
  • Rectangular Channel
  • Rectangular-Round
  • Rectangular-Triangle
  • Semi Circle
  • Semi Ellipse
  • Trapezoidal Channel
  • Triangular Channel

Additional information about all the available conduit shapes is provided in this wiki article and the Help section of the software.

Note that the Irregular Channel and Irregular Closed Channel options can be used to enter a custom station vs. elevation curve, enabling you to model any shape.

Step 3

Input the geometrical parameters (height, span, width etc.) necessary to define the shape. For the irregular channel and irregular closed section options, you would define the rating table for your specific shape, which can be pasted in using CTRL+V if needed, from an external source.

Once the shapes/size are created, if you would like to use them as standards for other projects, you can export them to the conduit engineering library. See more: Modifying and using Engineering Library Data

Step 4

In the properties of your conduit or cross section, choose the Catalog as the type, then select the catalog class and size/material as applicable.

NOTE: if you were already using a catalog conduit and change the shape dropdown of the existing catalog class, you will either need to re-pick the Size from the conduit properties dropdown, or global edit from the flextables (otherwise the conduit will still show the old shape and dimensions, despite the numerical solver using the new shape and dimensions.

See Also

Can constraint based design size open channels?

Modifying and adding entries to Engineering Libraries

Modeling Arch section shapes in SewerGEMS