Vertical design of a pressure network has two steps: the initial layout, followed by refinement of that layout.
For pressure networks, the initial vertical design information is created along with the horizontal design when you are doing the plan layout. During the plan layout, you can specify a Reference Surface and Cover value in order to place the water main at the minimum required depth below (or distance above) the surface. These settings are what allow a 3D model to be created from the very beginning of the design process.
You can then refine the vertical layout in profile view as needed to achieve a best path.
For information about the workflow when working with pressure networks in profile view, see
Workflow: To Refine the Layout of a Pressure Network in Profile View.