Abstract: A fluid pressure regulating valve apparatus for controlling either upstream or downstream fluid pressure includes a lower housing including a lower interior space and an upper housing including an upper interior space which is separated from the lower space by a deformable diaphragm. The diaphragm and lower space together define a substantially smooth, generally void free fluid receiving cavity with which first and second conduits are connected. The first conduit includes a constriction and the second conduit is angled relative to the first conduit. A valve is provided including a valve closure member movable between flow-permitting and flow-preventing positions. An upper stem element is connected to the diaphragm and extends through the upper interior space to an upper end disposed exterior of the upper housing such that pressure regulation and regulator adjustment may both be carried out from outside the lower housing.