Pentek 150233, Big Blue, 1" In/Out, #20 Blue/Black, HFPP, w/ PR Large filter housing for high-flow and heavy sediment applications Reinforced polypropylene sump for strength and chemical resistance Use with a 20 x 4-1/2 filter cartridge (sold separately) Pressure relief button for easier cartridge replacement Initial pressure drop of 1 psi at a flow rate of 15 gpm