preventing the flow of a fluid through a valve seat into a fluid pressure chamber within a valve body, utilizing a flexible resilient diaphragm forming a wall of said chamber when said diaphragm is not mechanically deflected;

deflecting a self-restoring section of said diaphragm having an outer edge to introduce fluid into said fluid chamber;

flexing said self-restoring section in response to pressure changes within said chamber;

controlling the flow of fluid through said valve seat into said chamber with a valve element integrally formed with the self-restoring section and composed of self-restoring material in a manner such that increasing the pressure in said chamber moves said valve element towards said valve seat and decreasing the pressure in said chamber moves said valve element away from said valve seat;

allowing fluid to flow from said chamber to an outlet in said valve body;

adjusting the pressure by rotating a cover having an adjuster fixed for rotation therewith relative to said valve body, said adjuster deflecting said diaphragm by contacting it at a position spaced a distance from the outer edge of the diaphragm in a manner to control the flexing of said diaphragm section to obtain a desired outlet pressure;

defining a plurality of angular positions relative to said valve body; and

positioning said cover in one of said plurality of angular positions.