On this same topic (water), I saw the following question posed today to Tom Lehmann at PMQ about distilled water, and Tom's response:
What effect does using distilled water in dough formula have, all other ingredients and factors being the same? I understand the PH is 7, good for dough production, but is the lack of minerals in distilled water a factor? I am going to produce dough from a mobile concession trailer so am looking for a consistent water.
As opposed to tap water, it will produce a softer, slightly sticky dough. This is easily corrected by using less water in the dough. Once this is done, there will be no further changes in the dough or finished product as a result of using distilled water. It should work fine for you.
Tom Lehmann/The Dough Doctor