Abstract: A regulator valve includes a valve body defining a central bore with a longitudinal axis. A rod couples to a diaphragm and slides along the longitudinal axis within the central bore. The rod has a planar end. A spring, such as a helical spring, mounts in the central bore and engaging the rod. One or more parallel passages are formed in the valve body extend parallel to the bore. One or more slots are formed in the valve body, each of the one or more slots connecting one of the one or more parallel passages to the central bore. The regulator valve may be used in a pumping system as a pressure regulator.