A check valve is a vital item, installed in support of automatic shutdown valves and safety devices. Its purpose is to prevent and protect against the consequences of unintended reverse flow (either a pressure or vacuum application). The Check Valve provides high integrity first-line defense in the event of unwanted reverse flow and operates in advance of, or in conjunction with safety devices. It is immediately responsive and fast acting in its closure, thereby maximizing protection to prevent or minimize the adverse effect of any backflow. Available in 1.25", 1.5", 2", 2.5", 4", and 5".