When you define the sanitary run as an offset or a home drain, the plumbing module performs the sizing calculations using the information on the Offsets tab in the sanitary plumbing line sizing table (pipe sizing table), whose definitions can be found in Style Manager.
Most sanitary systems are found in buildings that contain multiple floors. Each floor of the building is typically represented in a separate drawing. When sizing a sanitary system that spans multiple floors, you must size the plumbing lines for each drawing separately, starting from the highest floor and working downward. You can then reference the individual calculation values from the higher floors as you perform sanitary plumbing line sizing on the lower floors. For more information, see To Size Sanitary Plumbing Lines for Multiple Floors.
The software does not distinguish between a horizontal offset and a horizontal branch. Therefore, you might want to create a style to represent a plumbing line that is a horizontal offset. For example, you could create a style called Black Pipe - Horizontal Offset, and select this style from the list on the Properties palette when you add the plumbing line.