It’s been almost three years since Flint’s water crisis began. What have we learned?

In 2014, the city of Flint, Michigan changed the source of its water from the city of Detroit to the Flint River. But in the transition to river water, officials didn’t implement proper anti-corrosion measures. Lead leached from old pipes into the water supply, and in some homes, lead levels measured 10 times higher than the limit set by the Environmental Protection Agency.

Last month, lead levels in Flint's city water finally tested below federal-action level. But residents are still being cautioned to use filters on their faucets, or to drink bottled water.

Flint’s current water infrastructure has been damaged by corrosion, experts say. And the ongoing cleanup in Flint holds lessons for other American communities, many of which still have old lead pipes in their underground networks.