Portland has great water compared to most cities. We use Portland tap water and run it through a filter we replace every 6 months.
If you are in a municipality that has too much chlorine, fluorine, or other chemicals you may want to use multiple filters or consider bringing in water for brewing somehow.
Water is very important. Some brewers choose their location based on the water available. Wouldn't it be great to have spring water to brew with?
Number one rule is that your water should taste good before you brew with it. And know that the better the water, the better the booch.
I have heard of problems using well water with too high of mineral content, and also problems with over-chlorinated city water.
If you are brewing at home, just buy a gallon of bottled spring water. Usually this is only $1-2 and it is sterile so you can brew a tea concentrate and add the cold water to cool it down. Faster brewing! And the water will be great so it is worth the dollar.