When pumping in relay, how many pounds should the supplying pumper supply plus friction loss?

In firefighting operations, particularly during relay pumping, it's essential to ensure that the supplying pumper operates at a pressure that can effectively overcome the friction loss in the hoses as well as provide an adequate supply of water. The correct range indicated is between 20 to 250 pounds per square inch (psi).

This pressure range is optimal because it allows the supplying pumper to maintain a strong and effective flow of water across the distance of the hose layout while accounting for pressure losses that occur due to friction in the hoses. The choice of a lower bound of 20 psi is significant, as a minimum of this pressure is typically necessary to overcome initial resistances and ensure efficient water delivery. On the upper end, 250 psi allows for robust delivery even in longer or more complex setups where friction loss may be more pronounced. Thus, aiming for this specific pressure range is key to ensuring effective relay operations during firefighting efforts.