The very unfortunate exerience of Flint MI also happened in Tucson AZ except that we did not have a Lead problem. All that happened was that a lot of steel and iron pipes were destroyed and that horrible rust filed water came out of the faucets.
It is important to understand what the problem is. It is not the failure to add a rust preventative chemical to the water. This is about the Calcium saturation of the water. This is usually called the Langelier Saturation index [LSI]. When this is positive, the water produces scale, when it is negative, the water is corrosive. This le3ads to the obvious conclusion that water should always be treated to have a slightly positive LSI. About +1 is usually recommended. Doing this is not complicated and does not require expensive chemicals. It is just like it is done for a swimming pool, Sodium Bicarbonate (baking soda) is used to raise the basic alkalinity and then Sodium Hydroxide, Calcium Hydroxide, or Hydrochloric Acid are used to adjust the pH.
What happened in Flint and Tucson is a worse situation. The water supplied through the system for years had a positive LSI and they some idiots that didn’t know about the LSI of water and its importance, switched to water with a negative LSI. What happened was that the water dissolved the accumulated scale in the pipes and with it all of the accumulated corrosion from many years. So, it was worse than just starting out with new pipes and water that would corrode them.
I find it most surprising that the people in charge of the Flint and Tucson water treatment didn’t know about the LSI and the need to adjust it. In Flint it was supposedly a matter of money. However, in Tucson, a lot of money was spent on a new water treatment system for the switch from well water to Colorado River water but no though was given to adjusting the LSI.
It appears that the failure to properly adjust the LSI of drinking water may be causing contamination problems in many cities.