Chlorine is often added to public drinking water in order to sterilize it. For fermentation purposes, this can cause trouble. When you use chlorinated water in a brew, some of the microbiotic constituents will die or weaken. The kombucha will take much longer to ferment, and its taste will be unbalanced, or perhaps entirely unfamiliar.
Fortunately, chlorine is easily removed from drinking water. It will simply evaporate if you let the water for your ferment sit uncovered for 24 hours.
Alternatively, some kombucha fanatics use bottled water, or draw from a separate water line or well.