Food and Entertaining What are the steps of filtration? What is a 4 stage water filtration system? 4 stage water filtration system. Ultra filtration down to 0.01 micron. Easy under sink installation. Great tasting water with activated granular carbon filter. Individual cartridges for each stage. What are the 4 main steps to water treatment? - Coagulation and Flocculation. ... - Sedimentation. ... - Filtration. ... - Disinfection.