When water suddenly stops moving through a hose, what is the result?

• A. Water hammer
• B. Cavitation
• C. Siphon surge
• D. Backflow

Answer: (A)

When moving water is forced to stop suddenly in a confined hose, a rapid pressure surge is created as the moving fluid’s momentum is arrested. This impulse travels through the line as a pressure wave and can produce a loud banging and place stress on the hose, fittings, and pump components. That sudden pressure rise is the classic water hammer effect.

Cavitation isn’t the same phenomenon; it happens when local pressure drops below the fluid’s vapor pressure enough to form vapor bubbles, which is a different mechanism tied to extreme low-pressure regions. Siphon surge relates to pressure changes in siphon systems and is more about flow in a siphon than a sudden stop in a simple hose line. Backflow describes a reversal of flow, not a pressure spike from stopping flow abruptly.