The Vac-Alert Model VA-2000S is a Safety Vacuum Release System (SVRS) designed for submerged suction applications. Submerged suction in this case applies to all applications where the circulating pump suction is below the level of the pool water surface. This unit incorporates a 0.375 Inch diameter orifice opening installed below the surge tube section. This orifice opening is sized to provide a limited amount of pump start-up surge protection, while at the same time allowing enough air into the piping system to insure dissipation of the dynamic suction force caused by the circulating pump