To bring an additional pump online in a multi-pump system, what sequence should be followed?

• A. Start motor
• B. Open discharge valve first, then suction
• C. Open suction valve, then gradually open discharge valve
• D. Close suction valve and restart

Answer: (C)

Bringing an extra pump online safely hinges on priming the pump and easing the system into operation. Start by opening the suction valve to let fluid reach the pump inlet and establish flow. This ensures the pump is primed and there’s liquid at the inlet, which helps prevent cavitation and a dry run as the motor starts. Once flow is confirmed, gradually open the discharge valve to ramp up pressure and flow in a controlled manner. This gradual opening avoids a sudden surge that can cause water hammer, pressure shocks, or strain on the piping and fittings.

Opening the discharge valve first or starting the motor without a primed suction path can lead to dangerous conditions like cavitation, pump damage, or piping stress. Closing the suction valve and restarting would again disrupt priming and require re-priming, adding risk and downtime.