Where did you get that 99% figure from? Because I suspect you made it up.

Especially since:

One-fourth of Americans currently receive water from a source that violates the Environmental Protection Agency's (EPA's) Safe Drinking Water Act.

https://www.multipure.com/purely-social/science/top-10-states-worst-public-water-ratings-united-states/

More information:

https://www.science.org/content/article/millions-americans-drink-potentially-unsafe-tap-water-how-does-your-county-stack

And then there are the substances which municipal water supplies don't even need to get out of their water-

https://en.wikipedia.org/wiki/Drinking_water_quality_in_the_United_States#Substances_for_which_there_are_no_federal_standards