On the pump operator's panel, when three lines are in use and one line is shut down, what is the expected overall reaction?

On the pump operator's panel, when three lines are in use and one line is shut down, what is the expected overall reaction?

• A. All of the above
• B. Only increase
• C. No change
• D. Only decrease

Answer: (D)

When three lines are in use and you shut down one, you reduce the total water demand and the friction losses in the remaining lines. With the same pump speed (RPM) and throttle setting, the pump operates at a lower point on its system curve, so the discharge pressure and the flow through the remaining lines decrease. In short, removing a parallel path lowers the load on the pump, leading to a decrease in pump discharge pressure (and overall flow through the system). That’s why the expected reaction is a decrease.

When three lines are in use and you shut down one, you reduce the total water demand and the friction losses in the remaining lines. With the same pump speed (RPM) and throttle setting, the pump operates at a lower point on its system curve, so the discharge pressure and the flow through the remaining lines decrease. In short, removing a parallel path lowers the load on the pump, leading to a decrease in pump discharge pressure (and overall flow through the system). That’s why the expected reaction is a decrease.