Abstract: A control valve in which the bonnet is removably fixedly attached to the valve body by a retained bolt and slot arrangement in such a way as to fix the marginal edge of the diaphragm main valve therebetween. The diaphragm defines with the bonnet a control chamber having an inlet control passage leading thereto from the valve body inlet and an outlet control passage leading therefrom to the valve body outlet. A control valve seat in the outlet valve seat is controlled by a solenoid plunger valve element in such a way as to afford either manual or electrical solenoid operation by virtue of a manually movable member mounting the solenoid assembly on the bonnet. An adjusting knob member is mounted by a snap fit on the bonnet in laterally offset relation with respect to both the main valve and the solenoid assembly.