As sea level rise drives saltwater farther inland, drinking water supplies of many coastal cities will be contaminated. This talk evaluates the shifting the location of “salt lines,” the zone where coastal freshwater meets the ocean, and the implications for drinking water management. It tells the story of changing salt lines in the Delaware River, located in the mid-Atlantic region of the United States, and the drinking water in Philadelphia, Pennsylvania. First, the talk summarizes historic salt flows and contemporary salt challenges in the Delaware, revealing Philadelphia’s need to manage salinity at its drinking water intakes. Then, the talk discusses how extreme events, which can force saltwater farther inland rapidly, may require different management responses than the slower change of sea-level rise. It suggests layered strategies for managing salt: accommodating periods of short-term water loss, while fundamentally adapting to long-term salinization. It discusses both technical and social solutions for adapting to salt, revealing that most of the available solutions will be difficult and costly to implement. The talk concludes by asking how to best scale adaptation to salty drinking water and implement reasonable, affordable solutions.