Most places are still putting fluoride in water, which at one point was thought to be beneficial for teeth, but has since been proven it doesn't have any benefits to teeth health except while at a very young age, and even then, too much actually causes the exact thing it is supposed to prevent; enamel decay. Buy a ZeroWater purification device, may not remove everything, but still better than drinking from the tap.

https://www.hsph.harvard.edu/magazine/magazine_article/fluoridated-drinking-water/