A passive check valve system according to the present disclosure includes a vacuum breaker (104) operatively connecting a wetwell (102) and a drywell (100). A discharge pool (110) of water is provided in the drywell (100). A housing structure (106) is provided in the drywell (100) to enclose the vacuum breaker (104). The housing structure (106) has one or more discharge pipes (108) extending into the discharge pool (110), and the volume of the discharge pool (110) is greater than an interior volume of the one or more discharge pipes (108).