How are horizontal and vertical drains defined in the UPC?

The definition of horizontal and vertical drains in the Uniform Plumbing Code clearly identifies horizontal drains as pipes that are installed in a level or nearly level orientation. This means they run parallel to the ground, enabling effective flow and drainage of wastewater. On the other hand, vertical drains are characterized by their installation in an upright position, which is crucial for the proper functioning of certain drainage systems, especially those that facilitate the movement of materials downward due to gravity.

This distinction is fundamental for understanding plumbing systems design and ensuring that the drains are installed correctly to facilitate optimal drainage and function. The other options do not align with the standard definitions set forth in the UPC, as they introduce criteria that are either overly restrictive or incorrectly associate drain types with maintenance requirements and specific uses.