Yup, some infrastructure is ancient. From memory, correct me if I'm wrong, it was relatively safe in e.g. Flint because an inner lining of limescale had formed,

Yup, some infrastructure is ancient. From memory, correct me if I'm wrong, it was relatively safe in e.g. Flint because an inner lining of limescale had formed, but they changed something in the water causing that lining to deteriorate. But redoing infrastructure is a huge and expensive undertaking, also given that 100+ years ago they weren't as diligent in mapping out things underground and they put sewage, electricity and internet in the same ground since then. IIRC an in-between solution is lining the pipes with an inner plastic one (they have Ways), but that may not be possible everywhere and reduces the flow capacity. Anyway there's 2.2 million miles of water piping in the US apparently, that'll take a while.