J.L. Wingert stocks the quality line of valves made by Griswold Controls suitable for a wide variety of HVAC and industrial applications. & nbsp; Automatic flow control valves can be used in both open and closed systems, for flows from 0.33 to 17,000 GPM, and in pipe diameters of 1/2 to 30 inches. & nbsp; Griswold diaphragm valves come actuated, hydraulically self closing, pressure regulated, solenoid actuated, and liquid level controlled.