Which valve is designed to prevent backflow in a piping system?

• A. globe valve
• B. check valve
• C. gate valve
• D. ball valve

Answer: (B)

A check valve is designed to prevent backflow. It allows fluid to flow in one direction, and its movable element (disc, flap, or ball) is pushed open by forward flow. If flow reverses, the element is forced back onto its seat by gravity or upstream pressure, sealing the path and stopping reverse flow. This automatic, passive action is ideal for protecting pumps, piping, and connected equipment from backflow contamination or damage. Other valves regulate or isolate flow (globe for throttling, gate for isolation, ball for quick shut-off) but do not inherently prevent reverse flow like a check valve does.