What is the maximum sprinkler spacing between sprinklers on a branch line under standard conditions?

• A. 12 ft
• B. 24 ft
• C. 30 ft
• D. 40 ft

Answer: (A)

In a foam‑water system, spacing on a branch line is driven by the need for overlapping spray patterns and maintaining the required discharge density to create an effective foam blanket over every part of the protected area. Under standard conditions—no drafts, no obstructions, normal temperature—the distance between sprinklers must be small enough so that every point is within the reach of at least one sprinkler and the branch line pressure losses don’t reduce the foam concentration below the design requirement. This typically means using spacing equal to the nominal coverage footprint of a single sprinkler, ensuring complete coverage and the proper density throughout the protected zone. If you space sprinklers farther apart, gaps can form and the foam concentration can fall below what’s needed, reducing the system’s effectiveness.