A filter assembly is provided that includes a hood, a drain manifold, a filter disposed between the hood and the drain manifold, a drainage space that is disposed between and in fluid communication with both the filter medium and the drain manifold, a check valve that is configured to permit air to escape but not to enter the drainage space so that a siphon can be established that draws additional fluid through the filter medium and into the drain manifold, the siphon continuing until air entering the hood disrupts the siphon, and a check valve cap that is configured to permit air to escape the check valve while preserving an air-filled void above the check valve when the filter assembly is submerged.