What is the minimum residual pressure that should be maintained on the master intake gauge during pumping operations?

In pumping operations, maintaining a minimum residual pressure on the master intake gauge is crucial for ensuring an adequate flow of water and the efficient operation of the system. The correct answer indicates that a minimum of 20 psi (140 kPa) should be maintained.

This pressure is important because it helps ensure that there is enough pressure available to prevent cavitation, which can occur if the pressure drops too low. Cavitation can decrease the efficiency of the pump and potentially cause damage. Moreover, a baseline of 20 psi ensures that there is sufficient pressure to deliver water to the necessary locations, especially when considering the friction losses that may occur in hoses and fittings.

Options that suggest lower residual pressures fail to provide the necessary threshold needed for reliable operation and could lead to issues during pumping. Thus, the recommendation for at least 20 psi (140 kPa) strikes a balance between operational effectiveness and system protection during pumping operations.