What is the maximum number of fixture units that can be connected to a 3-inch building drain branch sloped at ¼ inch per foot?

• A. 30 fixture units
• B. 36 fixture units
• C. 42 fixture units
• D. 48 fixture units

Answer: (C)

A 3-inch building drain can accommodate a specific maximum number of fixture units based on plumbing codes and standards. In the IRC (International Residential Code) and the Uniform Plumbing Code, the maximum number of fixture units allowed on a 3-inch drain is determined by factors such as the drain's diameter and slope.

For a 3-inch building drain, the maximum allowable fixture units is typically defined in tables that take into account the slope of the drain. When sloped at ¼ inch per foot, a 3-inch drain can effectively handle up to 42 fixture units. This capacity ensures that drainage is efficient, allowing for proper wastewater removal while minimizing the risk of clogs and backups.

Understanding these values is crucial for plumbing inspections to ensure that installations meet safety and performance standards. Thus, 42 fixture units is the correct interpretation of the plumbing code in relation to the specifications provided for a 3-inch drain with that slope.