My quote is not from a book, but rather than lengthy tutorial on brewing water from the Bru’n Water spreadsheet. It’s one of several water calculators that many of us use to make mash and sparge water predictions/ adjustments. It has proven to be very accurate when using either RO or distilled water and an accurate grain bill. The starting pH of distilled and RO water are pre-determined figures in the spreadsheet which are relatively insignificant. I don’t know how you manipulate your brewing water or what tools you use to do so, but it seems that your question might be better answered by some of our resident water experts such as @mabrungard or @Silver_Is_Money .