Adding Slope Drainage Lines to CADmep with Design Line

This blog post was originally written for the Managed Design blog. Managed Design is now a U.S. CAD company, so please check back here at for more written articles from Philip Charlson and our new U.S. CAD Minnesota team.

Creating domestic piping type lines within CADmep is a simple task for most fabrication software users. However, some people tend to have difficulties when creating sloped pipe for waste or vent-type piping. Below is my process for adding slope drainage lines to CADmep with Design Line.

Drainage Pic 1

After a user has created their fabrication piping at an elevation they will want to change the sloping to match what will be out in the field so that they have correct lengths and parts.

drainage pic 2

Once the parts are laid out in a plan view the user will want to switch over to an isometric view representation.

Go to the Line pulldown and select Drainage Tool and then click on the Define Source button near the top of the dialog box. You will want to select the lowest point of the Design Line system for your waste line. You will see the node point change its position. This will identify the direction of the flow.

drainage pic 3

Next you will go back to the Drainage dialog box and pick Select positions to fix. If this is not displayed make sure that Fix Selection is checked under the Run Heights area. This means the risers that you have set to your fixtures will be locked into the specific height so when you add a slope they remain the same elevation. You can pick multiple risers in this step. Click enter after your selections.

drainage pic 4

Now to set the fall ratio or the slope that you want to define.  Go back to the Drainage dialog and near the bottom you will see the Fall (1:??) designation with a drop down list. A selection of 40 would be equivalent to 1/4” slope and 80 would be equivalent to 1/8” slope. If you need to add additional fall selections, the Add New Fall button is to the right of the drop down selection box. It will ask you to enter the Set to 1 in XX: for a designation that you want to appear. When you have this set click OK.

drainage pic 5

If you switch to a side view orientation you will see now that your waste lines are now sloped to what you just designated and you will now get correct lengths and fittings based on the settings you just created.

drainage pic 6

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