Use the Pipe Placement tools to draw pipe in your model.
When the Pipe or Pipe Placeholder tool is selected, the Modify | Place Pipe tab provides the following options for placing piping:
Create Riser: lets you create a vertical duct or pipe while working in the editor. Pick a start point and elevation, choose a new elevation in the Properties palette, then click Create Riser. You can also use it while laying out ducts or pipes by changing the elevation and clicking Create Riser to add a vertical segment.
Inherit Elevation: inherits the elevation of the element being snapped to.
Inherit Size: inherits the size of the element being snapped to.
Slope Off: draws pipe without slope.
Slope Up: draws pipe with slope up.
Slope Down: draws pipe with slope down.
Show Slope Tooltip: displays slope information while drawing sloped pipe.
Add Vertical:sloped pipe connects using the current slope value.
Change Slope: sloped pipe connects directly regardless of the slope value.