I think the problem is not fluride but chlorine. Where I live (Philadelphia) the tap water tastes strongly of chlorine, I can imagine it imparting a flavour on food.

(http://www.phila.gov/water/Fact_Sheets.html#fact17)

Perhaps, but remember that chlorine is meant to kill germs, so it must also have a negative impact on the fermentation process; yeast are just good germs, after all.

You can fill a pitcher with water, and let it sit out overnight in the refrigerator. All the dissolved chlorine will evaporate out.

Yes, that is true about Philly water-- until recently I worked there, and I'm about 20 min. S of you over the DE State line.