They actually changed the source of their water, for a few reasons, but the lead pipes behaved OK when used with water from the Detroit system, once they switch

They actually changed the source of their water, for a few reasons, but the lead pipes behaved OK when used with water from the Detroit system, once they switched to drawing from the flint river (while a pipeline to Lake Huron was being constructed) the more corrosive water from the flint river sort of “unleashed the leaching” of lead from the pipes. So, it’s about a bit more than just lead pipes. Here’s a good article explaining https://www.nrdc.org/stories/flint-water-crisis-everything-you-need-know#summary https://www.nrdc.org/stories/flint-water-crisis-everything-y...