Elevated Lead Levels in Water Supply

Elevated Lead Levels in Water Supply

I understand that lead solubility in water is very low, so how does lead from lead pipes get into the water supply? Does the lead from the lead pipe react with the carbonates associated with the alkalinity of the water or with the added chlorine as a disinfectant? If there is any lead (soluble and particulate) in the water source, it is typically removed through the various stages of the water treatment process. I am therefore curious - where did the lead, e.g. in the Flint incident, come from? There was a discussion about lead leaching out into the water supply, but where did it come from and why were the lead levels not reduced? Please explain the lead corrosion chemistry mechanism in simple terms and include any illustrations with references.