What is the recommended pressure that a relaying pumper should maintain to ensure the receiving pumper is adequately supplied?

The recommended pressure that a relaying pumper should maintain to ensure the receiving pumper is adequately supplied is 20 psi. This pressure is considered optimal for establishing an effective supply line between the relaying pumper and the receiving pumper, ensuring that there is sufficient flow and pressure to meet the operational needs at the scene of a fire incident.

Maintaining 20 psi allows for the necessary friction loss in the hose and ensures that the receiving pumper receives adequate pressure to operate its hose lines effectively. This pressure helps to balance the logistical challenges and ensures that water is available where it's most needed without overwhelming the system or creating excessive wear on the equipment.

Using other pressures, such as 10 psi, might not provide enough head pressure to counteract the friction losses that occur over long distances or through multiple hoselines, leading to an inadequate water supply. Similarly, while 30 psi and 40 psi may create additional pressure that seems beneficial, these pressures can lead to unnecessary strain on the apparatus and hose lines, and could also create a high risk of equipment failure or damage, especially in extended operations. Thus, 20 psi strikes the right balance for effective water relay operations.