Designed for submerged suction applications where circulating pump suction is below the pool water surface level.  Incorporates a 0.375″ diameter orifice below the surge tube section to provide limited amount of pump start-up surge protection while allowing enough air into the piping system to insure dissipation of dynamic suction force caused by the circulation pump. Also utilizes a check valve assembly equipped with 0.25 pound spring minimize the sealing force of the check valve and a non-vented poppet to insure that water from the circulating system, under positive hydrostatic head condition, does not migrate up to the SVRS.