The Best water for a successful Water Fast

I've been doing a lot of thinking about water leaving a residue in our bodies, and therefore hindering the most successful Water Fast.
I've just purchased a Berkey Water Filter and a Precision Water Distiller (made in Canada). I may be a fanatic about this, but I want my Water to be as Pure as possible...without any chemicals, or solids. I've seen the crud that is left behind in a water distiller, and I don't want any of it in my Body.
Who here is concerned enough about their water to do something about it??.....WY