The Vac-Alert Model VA-2000L is a Safety Vacuum Release System (SVRS) designed for suction lift applications. Suction lift in this case applies to all applications where the circulating pump suction is either at or above the level of the pool water surface. This unit incorporates a 0.17 Inch diameter orifice opening installed below the surge tube section. This orifice opening is sized to prevent nuisance tripping of the SVRS unit caused by high vacuum surges typical of many pump start-up conditions