Below is a list of AWWA Butterfly Valves manufacturers from King of Prussia, Pennsylvania. AWWA butterfly valves are flow control mechanisms that use rotating discs to open and close the valve within a water pipe. These valves are certified to meet standards put in place by the American Water Works Association. Butterfly valves consist of a round disc or vane that is attached to a control lever or wheel, which when rotated as little as 90° will cause the disc to rotate and stand perpendicular to the flow of water through the pipes.