What does Schedule 40 refer to in plumbing?

Schedule 40 specifically refers to the wall thickness of pipes, particularly in PVC and other types of plastic or metal piping. The term "schedule" denotes a standardized set of specifications for the pipe, which includes the wall thickness and, indirectly, the pressure rating that the pipe can handle.

For example, Schedule 40 PVC pipe has a certain thickness for a given diameter, which makes it suitable for various plumbing and drainage applications. It's important for professionals and apprentices in plumbing to understand these specifications, as the wall thickness will influence the pipe's strength, weight, and suitability for different jobs. The other aspects mentioned in the question, such as pipe length, material type, and color, do not directly correlate to the term "Schedule 40." Understanding this designation helps in selecting the correct pipe for specific tasks and ensuring that plumbing systems function effectively and safely.