I do not know where your ...
Published by Parke Blair, Chairman at GeoSource Foundation
I do not know where your info is coming from but the more pure the water, the better, regardless of P.H. Value! Rain Water is about as pure as it gets, but I'm also unaware of ANYPLACE on the Globe where you can count on Rain Water as your sole supplier without mass storage/storage tanks which are cost prohibitive if even available in remote areas.
Other Technologies you can successfully implement affordably along with your Rainwater Harvesting are: Solar Distillation Panels (can purify almost any kind of contaminated water, have been used to recycle Frac Water, also serve double duty & capture Rain Water), AWG = Atmospheric Water Generators, they capture & create pure water from the moisture in the air & are proven everywhere on the Globe, even in Deserts!
For more info or to begin a dialogue on this topic, please feel free to contact us;
Geosource Foundation in Malibu, California USA
(805) 410-2372
You may also want to see;