All intake and discharge valves 3 inches or greater must be equipped with what type of control valves?

• A. Slow acting control valves
• B. Fast acting control valves
• C. Manual control valves
• D. Proportional control valves

Answer: (A)

When large intake or discharge valves (three inches or larger) change position, they move a big flow of water. Opening or closing them too fast can create dangerous pressure surges—water hammer—that can damage pumps, piping, and fittings and endanger operators. A slow-acting control valve limits the rate of opening or closing, producing a gradual change in flow and pressure, which helps protect equipment and provides safer, more predictable operation.

Fast-acting controls would cause sudden pressure spikes, which defeats the purpose. Manual controls rely on the operator’s action and can introduce delays or inconsistent speeds, which isn’t ideal for large valves. Proportional controls offer adjustable response, but the requirement calls for a slow-acting type specifically, to ensure a controlled, conservative rate of movement on these sizable valves.