Hidden beneath the asphalt, miles of tubes snake through our cities. You can’t see it, but this infrastructure plays a huge role in how municipalities handle everything from wastewater to the H2O that streams from your tap. Despite its importance, much of the United States’ water infrastructure is outdated. Consider this: More than 750 cities in the United States still rely on combined sewers, a water management system that uses the same pipes to handle storm water, sewage, and industrial wastewater. During times of high flow (rain storms, for instance), water can exceed the tubes’ capacity and discharge into rivers, streams, or the ocean, creating some serious implications for water quality and human health.