A main body has a partition wall provided in the interior of the main body and a communication hole formed in the wall. A valve body is disposed in the main body to be movable between a first position and a second position. At the first position the valve body closes the hole, and at the second position the valve body opens the hole. A spring urges the valve body into the second position. An operating lever is connected in a universal-joint fashion to the main body. A cam is formed on the lever and slidably contact with a cam contact element disposed on the valve body in a position away from a plane including a center axis of the main body. A pair of grooves are formed on the lever at each side of the cam and extend along the plane. A pair of projections are provided on the valve body and inserted into the grooves. When the lever is rotated in one or the other direction in the plane by an external force, the valve body is moved between the first and the second position by the action of the cam. When the external force is removed, the lever rotated in a direction transverse to the plane and the projections are frictionally engaged with the lever from rotating in the plane.

A control valve with a three part, all plastic housing having an access opening through which a slide extends for operating the plastic valve element toward and away from the valve seat, the plastic valve element having an integrally molded plastic diaphragm clamped between parts of the all plastic housing and traversing the entire access opening, the slide being operated by a rotor, there being ramp shaped surfaces on confronting faces of the rotor and slide, and an adjustment nut for locating the rotor, slide and valve element relative to the valve seat.