I tried a Pur water filter when I first started growing hydro and was not happy with it at all. Originally the problem I had was that I could not stablilize the ph--it would go down etc but not stay there; no matter what. The filter took the ppms in my tapwater from 250 to about 100-150 which was fine but the ph remained a huge problem (ph in my tap water was 8--a Pur water filter actually took the ph to 10 which was NOT the answer I wanted) so I only use r/o water and I love it. We have a well by the way so it probably plays a pretty good role in the ph instability. (had the problem in my fishtanks too so I knew it would be a problem with growing). Good luck.