I have used the ZeroWater system for about two years. It was recommended as a favored option by the lab that tested my water. I like the system very much, especially the ability to measure the dissolved solid content using the included tool. My water tests at about 17 unfiltered. The ZeroWater filters reduce the count to 0, initially, gradually building back up to the 006 filter replacement level. I would rate the ZeroWater at a 5 except for the tendency for the filters to airlock, requiring maintenance to keep water flowing through them. (This happens fairly regularly).