Check valves are used in systems to prevent backflow. The valves can come equipped two different ways. The first way is with a floating ball in it that will check up inside the valve once the flow is stopped in the system. The other way this valve is manufactured is using a swing check method. The valve comes with a flap inside of it that will allow media to flow through a certain way then the flap will close once the flow is shut off to prevent the media from changing directions. This valve will not allow backflow into the system when installed properly. The check valve will come with an arrow on it to denote which direction the flow is allowed to move.