Abstract: Filter assemblies, filter modules, and filtration systems and methods.

Abstract: A filter cap includes a first end and a second end facing away from the first end. A first cylindrical projection projects from the first end of the filter cap and a second cylindrical projection projects from the second end. An annular recess is formed around the first cylindrical projection. The second cylindrical projection includes at least one peripheral groove for an O-ring and a plurality of radially inward extending ridges. A passageway extends through the first and second projections. The passageway has a first dimension in the first projection, a second dimension greater than the first dimension in the second projection near a distal end of the second projection, and a third dimension smaller than the second dimension within the second projection between the plurality of ridges.