Yes, I would say the "fatal flaw" is that it's chlorinated water. Chlorine can combine with malt phenol to form chlorophenol. A surprisingly small amount of this substance can give your beer a "medicinal" undesirable taste. I have never brewed with my tap water and this is why I never will. It's too bad because I hate having to buy those 2.5 gallon jugs of Ice Mountain natural spring water, but I do, and have never had a problem with this water. Take care....and my advice is stay away from chlorine.