An anti-siphon/regulator valve is provided. The valve includes a body having a cylindrical portion and a frustoconical portion extending from the cylindrical portion. The valve includes an inlet opening formed in a first end of the body on the cylindrical portion and an outlet opening formed in a second end of the body on the frustoconical portion. The valve also includes an inner multi-tapered aperture extending from the inlet opening and the outlet opening. The valve operates to regulate fluid flow from the inlet opening through the outlet opening based on the geometry of the multi-tapered aperture, and to inhibit flow from the outlet opening through the inlet opening because of that same geometry.