A few years ago we received a note in our water bill letting us know that our water tested too high for something and we shouldn't let infants or toddlers drink it. Our son was about one year old and we had started him on those transition cereals where you mix the powder with water. So we ended up having to buy water to use for him. I'd buy those big 2 gallon square just, they were far more space efficient that small round bottles.
We received no other notice letting us know when the water actually tested unsafe or no notice letting us know when it was safe again, real nice communication of our city at work.