What is a consequence of abrupt throttling during pump start or stop?

• A. Surges and potential pressure spikes
• B. No effect
• C. Reduces prime loss
• D. Improves nozzle quality

Answer: (B)

Abrupt throttling during pump start or stop creates hydraulic transients. When you slam the throttle open or shut, the flow rate changes suddenly, sending pressure waves through the piping. These waves show up as surges and pressure spikes, which can stress pipes, valves, and the pump and cause unstable discharge conditions. To avoid water hammer, throttle gradually and coordinate valve movements with the pump’s speed ramp.

The notion of no effect isn’t accurate because these rapid changes in flow induce noticeable pressure transients. Prime loss isn’t reliably reduced by abrupt throttling, and nozzle quality isn’t improved by a sudden change in flow—both are undermined by the resulting pressure fluctuations.