Dependin on how much stuff/tds your trying to filter out or how high your incoming ppms are I've done a few different things..I like a Blueboy in front of a Merlin for moderate ppms to get the super action I went thru a saline softener, charcoal charger filter, blue boy two canister, merlin, and then a UV scrubber before the storage tanks..that took my well water from 2600ppm down to 12ppm