There has been a lot of discussion concerning water purifiers lately. Seems most folk's water filters have a combination of sediment,charcoal filters & an RO membrane. My 4 stage purifier has the same filters but the last stage of contains deionizing resin. This resin contains Cation & Anion beads that absorb positive & negative charged ions. DI resins are common in water purifiers used in the aquarium field. My city water tests around 128 to 130 ppm's. With all new filters ,ro membrane & di resins, my filtered water test at 3 to 5 ppm's.Not pure H2O but close! I'm no Chemist by any means! I do think nearly pure water doesn't have a long shelf life. In simple terms it is highly reactive and quickly absorbs what it comes in contact with. Like gases in the surrounding air or anything added to it. I purify only enough water I need at the time . Also I fill any new plastic containers with filtered water several times & discard the water before actually using it. I was surprised at the big increase in ppm's of water in new containers. Anybody else out there use the di resin in their water purifiers? Any opinions on using nearly pure water in either hydro or soil gardens?