If residual drops over 25%, what multiplier applies to main flow?

If residual drops over 25%, what multiplier applies to main flow?

• A. 3X more
• B. 2X more
• C. 1X more
• D. 0

Answer: (D)

If residual pressure loss is over 25%, there isn’t enough pressure head left to safely boost the main flow. In this situation you don’t apply any extra multiplier to the main flow—the multiplier is effectively none, meaning you don’t increase discharge beyond the baseline. Pushing for a larger main flow when the system has already lost a large portion of its pressure would drop residual pressure further and could jeopardize the reach and stability of the fire stream. In other words, high residual loss signals that increasing flow is not feasible; you either maintain the current level or reduce demand until pressure recovery is possible.

If residual pressure loss is over 25%, there isn’t enough pressure head left to safely boost the main flow. In this situation you don’t apply any extra multiplier to the main flow—the multiplier is effectively none, meaning you don’t increase discharge beyond the baseline. Pushing for a larger main flow when the system has already lost a large portion of its pressure would drop residual pressure further and could jeopardize the reach and stability of the fire stream. In other words, high residual loss signals that increasing flow is not feasible; you either maintain the current level or reduce demand until pressure recovery is possible.