When I import perpendicular linework from AutoCAD using the WaterCAD ModelBuilder feature, a junction is created, but the lines are not connected.
This is what the imported linework looks like (the purple lines are pipes):
But node J-296 can be pulled away without impacting the vertical line:
Is there a way to get the WaterCAD ModelBuilder feature to import it as 3 pipes and one junction instead of 2? Or perhaps there is some manipulation I can do beforehand on AutoCAD?
You could adjust the source file to make sure something like this does occurs. However, there is a tool in WaterCAD that can help. The Batch Pipe Split tool can be used to make sure the nodes for perpendicular pipes are connected. This will split pipes where a junction is on a pipe but not connected to it.
To add to Scott's response. If you do want to address it in AutoCAD, you could split that polyline at the location of the Junction so that ModelBuilder will pick up on it. (I believe the "break" command in AutoCAD is what you would use).
As we discussed in this post, this can also be achieved by checking which lines are "polylines". Check to see if the vertical line is a polyline. If you draw perpendicular to this line you would get a junction only on the end of the horizontal line when imported via ModelBuilder. A quick way to check this in the drawing itself is to see if the selected polyline is selected as a whole. If you introduce a "break" as Rob suggested, you would see two separate lines when you select.
To have a junction at the end of a line the polyline or line should start or terminate at that location. In AutoCAD connecting (either perpendicular or anyway) to a polyline does not automatically split at that point since its a drawing entity. You would have to manually introduce a break to ensure that 2 or more lines terminate or begin at that point.