I’m a day short and a dollar late, But I use a RO filter on the well water here.
Well we use to use a built in filter/cleanse filter cause the water we had access to was poisonous and would kill us if no filters were used and it’s city water ……… somethin not right here
You live in Flint, Michigan?
My dear friend do not play with water safety. If you know or you are suspicious about it, it is better to use bottled water for drinking. Water hides so many dangers you cannot even imagine. There is no water company globally that will guarantee the quality of water you gain from your taps, they will guarantee only the quality that exits their factory 
. The way is long to get in your pipes and the problems might be many. All you have to do if you are not sure, is buy a kit for water testing and give it in 24 hours max to a chemistry lab for testing. But you have to be very exact to the procedure, so if you can afford it pay a chemist to do it for 99% results.
I recommend Big Berkey BK4X2-BB, this filter is great. It makes water quick and easy. Honestly, water tastes better with RO. The process of setting it up is time consuming and a bit difficult, but worth it!
No Illinois
Yeah I know which is why we had to use it . It’s a real long explanation but the water was safe with the filters but without it was positioning if you dank more than a glass a day but we don’t live there anymore thankfully 