What factor determines the minimum size of any building sewer?

The minimum size of any building sewer is determined by the total number of fixture units. This approach is consistent with the principles set forth in plumbing codes, which assign specific values to different fixtures based on their anticipated flow rates and usage patterns. Fixture units provide a standardized measure of the load that a plumbing system must accommodate, enabling engineers and plumbers to accurately size pipes and components.

By calculating the total number of fixture units, one can assess the expected demand on the sewer system and ensure that it is sufficiently sized to handle wastewater without risking backups or failures. Each type of fixture has a designated fixture unit value, which helps in deriving the cumulative load from all fixtures within a building. This is essential for ensuring proper drainage, minimizing potential clogs, and maintaining sanitary conditions.

While the type of building, number of stories, and size of plumbing fixtures are all relevant factors in overall plumbing design, they do not directly provide a systematic method for determining the minimum size of a building sewer like the total number of fixture units does. Understanding this relationship is crucial for compliance with plumbing codes and for ensuring effective wastewater management.