What term describes the transient pressure rise in piping due to sudden changes in flow?

• A. Looped mains
• B. GPM vs PSI
• C. Critical Path
• D. Surge/hammer

Answer: (D)

When flow in a pipe changes suddenly, the moving fluid can’t adjust instantly, and a high-pressure wave travels through the system. This transient pressure rise, caused by the inertia of the water and the pipe’s elasticity, is known as a surge or water hammer. It’s the phenomenon you observe when a valve slams shut or a pump stops abruptly, leading to pressure spikes, potential noise, vibration, and possible damage if not managed. The other terms don’t describe this dynamic: looping mains is a layout approach to influence pressure behavior, GPM vs PSI just describes the relationship between flow and pressure, and Critical Path is a project management concept. So the correct term for the transient pressure rise is surge/hammer.