DESC: Exclusive bump handle activates the mechanism causing the Flex-Tubes to instantly and uniformly clean themselves of dirt and filter powder \nSelf-venting design automatically expels any air that may be present in the system \nProven, patented Flex-Tube filter elements efficiently reuse the filter powder and dirt mixture forming a fresh filtering surface \nCombination pressure gauge and threaded inspection/service port is easy to read and remove when filter needs cleaning \nHeavy-duty filter tank injection-molded of high-strength Duralon™ for dependable, corrosion-free performance \nIntegral check valve prevents system backflow whenever pump is off \n