The internet is full of both debate and certainty about the best water to use to create a sourdough starter. Over the years, we’ve observed that chlorine kills microbes and that sourdough starter seems to thrive in mineral-rich and lower pH environments, but we haven’t tested these observations in a controlled experiment until now. This experiment doesn’t arrive at a definitive answer to the question asked, but we learned so much while doing it that we want to share the information and insights.

https://breadtopia.com/what-kind-of-water-should-i-use-to-make-sourdough-starter/