What is the maximum horizontal branch drain size that a 2 ½ inch diameter pipe can serve?

• A. 4 fixture units
• B. 5 fixture units
• C. 6 fixture units
• D. 7 fixture units

Answer: (C)

The maximum horizontal branch drain size that a 2 ½ inch diameter pipe can serve is associated with its capacity to handle fixture units, which are a measure of the probable demand or load from plumbing fixtures. In plumbing code, different sizes of pipe can service varying amounts of fixture units based on standards that take into account both the diameter of the pipe and the expected flow rates.

A 2 ½ inch diameter pipe is typically rated to serve a maximum of 6 fixture units. This sizing is crucial as it ensures that the drainage system can adequately handle the waste and prevent backflow or blockages, thus maintaining the integrity of the plumbing system. The determination of fixture units is based on empirical data and codes that provide guidelines for proper plumbing design.

By understanding fixtures and their unit equivalents, one can make informed decisions about sizing piping systems to ensure they meet local plumbing codes and prevent drainage issues.