Which type of valve obstructs water flow the least in water lines?

• A. Ball valve
• B. Gate valve
• C. Check valve
• D. Butterfly valve

Answer: (B)

The gate valve is designed primarily for fully on or fully off service and provides minimal resistance to the flow of water when fully open. Its unique design features a wedge-shaped gate that is lifted up into the valve body when opened, allowing water to pass through with little obstruction. This feature makes the gate valve highly efficient in applications where a straight flow path is necessary.

In contrast, other types of valves typically introduce more turbulence or resistance to flow when open. For instance, ball valves can also provide a relatively unrestricted flow, but they are less commonly chosen for applications where a gate valve might be more appropriate. Check valves are designed to prevent backflow and often have restrictions that can impede flow. Butterfly valves have a disc that rotates to control flow, which can cause some level of obstruction in the pipeline.

Therefore, the gate valve is the best choice when the priority is to obstruct water flow the least while maintaining the ability to quickly halt flow when necessary.