Abstract: A ball valve for a hydronic heating or cooling system, in which a purge port is integral with the valve body of the ball valve. The valve body that has an inlet and outlet port, and an interior passage configured to permit liquid to flow between the inlet and outlet ports. A ball element is supported within the valve body, the ball element having a flow passage extending there through, and the ball element being supported so that it can rotate from one position in which the liquid is able to flow through the flow passage, to a second position in which the liquid is unable to flow through the flow passage. An actuating shaft extends from the ball element through a first opening in the valve body to the exterior of the valve body. A handle connects to the actuating shaft for rotating the shaft and ball element.