Check Valve, also known as a one-way valve or Check Valves. Pipeline used to prevent reflux of a fluid valve. So pipeline fluid can only make one-way flow of fluid when the clock back, the flap valve can be shut down automatically to prevent backflow. According structure can be divided into two categories : elevating and spin-Kai (or a shake-flap). Former perpendicular to the valve flap valve passageway movements with Valve are generally designed as a cut-off valve and valve common. The latter is a flap valve around the sealing surface for rotating movement, resistance than elevating small, poor sealing performance.