A fuel water separator (FWS) filter that is configured to permit water to be drained from the water sump of the FWS filter without shutting off fuel flow to the FWS filter. A check valve is positioned between the water sump and the filter element. When the FWS filter is under vacuum (e.g. as in operation), the check valve can be closed to allow water to drain from the sump. The check valve can close automatically by floating on accumulated water in the sump until the water rises to a level where the check valve is closed. The check valve can also close by opening the drain valve of the FWS filter, which causes a differential pressure between the sump and the vacuum created in the filter element chamber, which forces the check valve to close.