When calculating the minimum pipe size for a potable water distribution system, which of the following factors generally requires the largest nominal pipe diameter to maintain adequate flow and pressure?

Question: When calculating the minimum pipe size for a potable water distribution system, which of the following factors generally requires the largest nominal pipe diameter to maintain adequate flow and pressure?

Answer options:

• Long runs of horizontal piping. ✅ High fixture unit count.
• Low static municipal water pressure.
• Multiple vertical risers.

Correct answer: High fixture unit count.

Explanation: A high fixture unit count indicates a high potential for simultaneous demand, requiring a larger pipe diameter to deliver sufficient flow rate while maintaining acceptable pressure. Long runs, low static pressure, and vertical risers certainly contribute to pressure loss, but a high fixture unit count is often the dominant factor in determining the overall pipe size for a distribution system.