Hi Amos, thanks for offering your expertise to this discussion! I imagine that chorine levels vary from one water supply to the next, so treated tap water may not cause harm in one area, but will in another. At our baking school we find that it's generally not a problem, but that if the water has a strong chemical odor, then it's worthwhile to let the water sit out in an open container for several hours. This allows the chlorine gas to dissipate. As you point out, a water filter can also be a good way to insure that your tap water is starter-friendly. Barb

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