What is the primary purpose of a check valve?

• A. To allow fluid flow in one direction only, preventing backflow
• B. To regulate pressure in a line
• C. To store hydraulic energy
• D. To cool the fluid

Answer: (A)

A check valve is built to let fluid move in one direction while blocking any return of flow. It uses a movable element—a disc, ball, or flap—that rests on a seat to seal the path. When fluid pushes forward, the pressure lifts the element and opens the passage. If the flow tries to go backward, the element is pressed back onto the seat (or held by gravity), closing the valve and stopping backflow. This protects pumps and equipment, prevents contamination or siphoning, and helps maintain proper system pressure by preventing unwanted reverse flow. It’s not meant to regulate pressure, store energy, or cool the fluid, which is why those functions are outside its purpose.