A filtration module assembly comprising: a vessel; a header coupled to an end of the vessel, the header including a housing having an open-ended upper end and a lower end; a filtration cartridge disposed within the vessel, the filtration cartridge including an upper end removably coupled to the lower end of the housing, wherein the filtration cartridge includes an external diameter smaller than an internal diameter of the housing, wherein the upper end of the filtration cartridge comprises an upper potting head, an end cap including a portion that mates with a complimentary structure defined by the inner wall of the open-ended upper end of the housing to removably engage with the housing, the end cap having a base portion, a reduced diameter mid portion and an upper portion, the outer wall surface of the reduced diameter mid portion of the end cap, the bottom surface of the upper portion of the end cap, the top surface of the base portion of the end cap, and the inner wall surface of the header housing defining a filtrate discharge passageway for filtrate to flow out of the vessel; the reduced diameter mid portion having an internal concave wall 127, a plurality of radially extending reinforcement ribs extending between the upper and lower walls and of the filtrate discharge passageway, base portion of the end cap having a central boss portion through which a shut-off passageway opens at its lower end, the base portion having a circumferential downwardly extending rib which bears against an upper peripheral edge of an annular adaptor, said upper peripheral edge including an inwardly extending circumferential lifting shoulder that abuts extending rib such that when abutting, rib and shoulder position base portion above the upper surface of the upper potting head to define a filtrate collection chamber positioned between the upper surface of the upper potting head and end cap. a vessel; a header coupled to an end of the vessel, the header including a housing having an open-ended upper end and a lower end; a filtration cartridge disposed within the vessel, the filtration cartridge including an upper end removably coupled to the lower end of the housing, wherein the filtration cartridge includes an external diameter smaller than an internal diameter of the housing, wherein the upper end of the filtration cartridge comprises an upper potting head, an end cap including a portion that mates with a complimentary structure defined by the inner wall of the open-ended upper end of the housing to removably engage with the housing, the end cap having a base portion, a reduced diameter mid portion and an upper portion, the outer wall surface of the reduced diameter mid portion of the end cap, the bottom surface of the upper portion of the end cap, the top surface of the base portion of the end cap, and the inner wall surface of the header housing defining a filtrate discharge passageway for filtrate to flow out of the vessel; the reduced diameter mid portion having an internal concave wall 127, a plurality of radially extending reinforcement ribs extending between the upper and lower walls and of the filtrate discharge passageway, base portion of the end cap having a central boss portion through which a shut-off passageway opens at its lower end, the base portion having a circumferential downwardly extending rib which bears against an upper peripheral edge of an annular adaptor, said upper peripheral edge including an inwardly extending circumferential lifting shoulder that abuts extending rib such that when abutting, rib and shoulder position base portion above the upper surface of the upper potting head to define a filtrate collection chamber positioned between the upper surface of the upper potting head and end cap.