Which device should be chosen to protect against reverse flow?

• A. Check Valve
• B. Pressure Reducing Valve
• C. Globe Valve
• D. Gate Valve

Answer: (A)

Preventing backflow automatically is the job of a check valve. It sits in the line and allows fluid to flow in the intended direction, but when flow tries to reverse or pressure changes push the fluid back, the sealing element (disc, ball, or flap) closes against the seat and stops the reverse flow. This passive one-way behavior protects pumps, meters, and downstream equipment from damage or contamination.

A pressure reducing valve is meant to maintain a set downstream pressure, not block backflow. Globe and gate valves control or isolate flow but do not automatically seal against reverse flow, so they aren’t reliable for backflow protection on their own.