A

Gravity pipes use natural elevation differences to transport wastewater or stormwater. They are cost-effective and easy to maintain but are unsuitable for flat or reverse-gradient terrain where sufficient slope cannot be secured.
Pressure pipes (including vacuum systems) use pumps or negative pressure to force flow, making them ideal for flat areas or uphill segments, though they incur higher installation and maintenance costs.
In PIPE Design Pro, the flow method is selected by setting the pipe type attribute in the Pipe Section DB (e.g., None, Pressure Pipe, Pipe jacking method)