Which of the following best describes a riser in plumbing?

In plumbing, a riser is best described as a vertical pipe that transports water, waste, or other fluids vertically between different levels of a building. Risers are essential for moving water supply or drainage from one floor to another, commonly found in systems that support multiple fixtures located at different heights. They are typically used for water supply systems in multi-story buildings, ensuring that each level has access to the necessary plumbing services.

The definition of a riser specifically highlights its vertical orientation, which is key to its function within the plumbing system. This distinguishes it from other types of pipes such as horizontal pipes, which run parallel to the ground, or pipes that connect fixtures, which may serve various functions but do not explicitly indicate direction. Additionally, a pipe that serves water to a single fixture usually describes a lateral or branch line rather than a riser, as risers typically service multiple points throughout a vertical space.