When pipes run underneath Design Master HVAC ductwork, it is possible to automatically convert them to hidden lines.
There is one limitation when doing this: the pipes must use a CONTINUOUS linetype. It is not possible to both use a non-CONTINUOUS linetype and automatically insert hidden lines.
To hide pipes below ductwork, use the Pipe Types commands.
Ribbon: DMP: Customization->Project Customization-> Pipe Types
Pulldown Menu: DM Plumbing->Customization->Pipe Types->Edit Project List
The last column is labeled Hide Pipes Below Ductwork. Check the box in that column for pipes that should be hidden.
Press the OK button to save your changes, then run the Update Drawing Graphics command to update all of the pipes that are already inserted on your drawing.
Ribbon: DMP: Customization->Project Customization->Update Drawing Graphics
Pulldown Menu: DM Plumbing->Customization->Update Drawing Graphics