What type of valve limits flow in one direction?

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

Answer: (B)

A check valve is designed to prevent backflow while allowing forward flow. It uses a movable element (disc, ball, or wedge) that seats against a face to form a seal when reverse pressure occurs, stopping any backward flow. When forward pressure pushes the element away from the seat, the valve opens and flow continues automatically, without external action. This self-acting, one-way behavior is exactly what’s needed to limit flow in only one direction, such as protecting a water supply from contamination or back-siphonage in piping systems.

Gate valves, ball valves, and globe valves are typically used for on/off control or throttling rather than automatic one-way flow prevention. They don’t inherently block reverse flow without being operated or configured with additional backflow protection.