What is a check valve? Check valves are generally installed in pipelines to prevent backflow. A check valve is basically a one-way valve, in which the flow can run freely one way, but if the flow turns the valve will close to protect the piping, other valves, pumps etc. If the flow turns and no check valve is installed, water hammer can occur. Water hammer often occur with an extreme force and will easily damage a pipeline or components. http://www.cnfuchuangvalve.com/