What is the clean-out requirement for horizontal drain lines less than a specified length?

In plumbing systems, the requirement for clean-outs is guided by the need to provide access for cleaning and maintenance of drain lines. For horizontal drain lines that are below a certain length, clean-outs may not be necessary because their short distance allows for easier access should clogging occur. The purpose of clean-outs is to facilitate clearing blockages, and in the case of shorter horizontal runs, the risk of clogs is typically lower and manageable without the need for additional clean-out access points.

By omitting clean-outs in shorter horizontal drain lines, the installation can be simplified, while still maintaining the overall effectiveness and safety of the plumbing system. However, it's important to note that code requirements may vary based on local regulations, so any decisions about clean-out installations should also take those governing codes into consideration.