On a horizontal waste branch ________ feet or less in length, the fixture outlet may be termed a cleanout.

When considering the definition of a cleanout in plumbing systems, the maximum length of a horizontal waste branch is important. A cleanout is an access point for cleaning and maintaining the drainage system. According to plumbing codes, a horizontal waste branch that is 50 feet or less in length allows the fixture outlet to be classified as a cleanout.

This classification is crucial because it enables plumbers to easily access the drainage line for any blockages or maintenance without having to dismantle the system. The specification of 50 feet is based on practical considerations of drainage and maintenance access, ensuring that fixtures can be effectively serviced if necessary.

In contrast, lengths greater than 50 feet do not typically allow for this classification because the distance could make it impractical for effective maintenance, thus requiring different designations or procedures for cleaning out clogs.