A check valve is a mechanical device that allows fluid to flow in one direction while preventing backflow. It is commonly used in various systems, such as plumbing, water supply, and industrial applications, to ensure that liquids or gases move in the intended direction. This helps maintain pressure and prevents contamination. Check valves operate using a simple mechanism, typically a disc or ball that moves with the flow of fluid. When the flow reverses, the disc or ball seals against the valve seat, blocking any backflow. This functionality is crucial in systems like pumps and heating systems to ensure efficiency and safety.