Statista’s summary is good, quote:
The Proceedings of the National Academy of Sciences has released a report exploring the geography of insecure water access in the United States. Describing safe, reliable, and equitable water access as a fundamental human right that proves critical to both health and livelihoods, the research found that 471,000 U.S. households lack universal access to “complete plumbing” – approximately 1.1 million individuals. “Complete plumbing” is currently defined as having access to piped hot and cold water and a bathtub or shower that is all located within the housing unit and used only by its occupants.
The problem is most evident in urban areas with 73 percent of all affected households located in cities and 47 percent in the country’s 50 largest metropolitan areas. That figure tracks closely with national population distribution. An estimated 220,300 households and 514,000 individuals do not have access to piped water within the 50 largest metros. The research found that New York has the highest number of both households and people without complete plumbing at about 27,000 and 65,000 respectively, followed by Los Angeles and San Francisco.