When starting centrifugal pumps, what should be true about the discharge valve?

• A. Start centrifugal pumps with the discharge valve closed.
• B. Start centrifugal pumps with the discharge valve fully open.
• C. Start centrifugal pumps with the discharge valve half open.
• D. Discharge valve position does not matter.

Answer: (A)

When starting a centrifugal pump, keep the discharge valve closed. This reduces backpressure so the pump can accelerate smoothly with a lower starting torque and current, and it helps prevent hydraulic shock when the pump first comes up to speed. Once the pump is running and the system is primed, you gradually open the discharge valve to the desired setting. If you start with the valve open, the pump has to push against full system pressure, which can cause a large surge in load, potential motor overload, and a risk of water hammer when the valve is later opened or the flow rapidly changes.