The rotary valve body (110) comprises a sealing cam (116,117) made of an elastic plastic, which is arranged on a rotationally symmetrical jacket surface of an area provided for the valve seat. The sealing cam rises over the radius of the rotationally symmetrical jacket surface, such that the circumference of the rotary valve body through the sealing cam is greater than the inner diameter of the valve seat. A feedthrough (112) is arranged in the rotary valve body. The feedthrough is extended from an opening in the rotationally symmetrical jacket surface in the area of the sealing cam to another opening in the rotationally symmetrical jacket surface of the rotating valve body. An independent claim is included for a valve system with a valve seat, in which three openings open into the gas lines.
