For Class I and Class III standpipes, what is the required riser size for buildings under 100 feet?

For Class I and Class III standpipes, what is the required riser size for buildings under 100 feet?

• A. 2 inches
• B. 4 inches
• C. 3 inches
• D. 6 inches

Answer: (B)

Standpipe vertical feeders must be large enough to deliver the required water flow with sufficient pressure to the farthest outlets on upper floors. For Class I and Class III standpipes in buildings under 100 feet, the standpipe riser is four inches in diameter. This four-inch size helps minimize friction losses along the vertical run, ensuring firefighters can obtain the needed flow at the outlets on upper floors without requiring impractically high pump pressure. While the individual outlets on each floor might be 2.5 inches for Class I (fire department use) or combined with 1.5-inch handlines in Class III, the vertical riser itself needs to be 4 inches for these shorter buildings to meet the overall flow and pressure needs. In taller buildings, larger risers or additional feeders would typically be used to maintain adequate performance.

Standpipe vertical feeders must be large enough to deliver the required water flow with sufficient pressure to the farthest outlets on upper floors. For Class I and Class III standpipes in buildings under 100 feet, the standpipe riser is four inches in diameter.

This four-inch size helps minimize friction losses along the vertical run, ensuring firefighters can obtain the needed flow at the outlets on upper floors without requiring impractically high pump pressure. While the individual outlets on each floor might be 2.5 inches for Class I (fire department use) or combined with 1.5-inch handlines in Class III, the vertical riser itself needs to be 4 inches for these shorter buildings to meet the overall flow and pressure needs. In taller buildings, larger risers or additional feeders would typically be used to maintain adequate performance.