Today I went and got 14 gallons of RO water. I had two 7 gallon containers when I got home I checked the Ph and it was about 5, which I thought was pretty low. I had previously had star san in them which has a low Ph but I poured it all out, and You always hear dont fear the foam so I was not worried to much about it. Tomorrow I am going to take a clean gallon jug and get some more and check to see if the residual star san in the containers is what brought the PH down or if the RO water really is that low. Does anyone use RO water and know what the Ph usually runs, I guess it may differ from area to area not sure though? I went ahead and brewed the mash ph looked fine?