Drinking Water Quality, System by System

Enter your ZIP code in the tool on this page. It resolves the ZIP to its county using the Census Bureau's ZCTA to county file, then lists every active community water system EPA's federal database records for that county, with size, water source and listed violation history. About 29 percent of ZIP codes cross county lines, and the tool shows every county the ZIP touches. Utility service areas do not follow county lines either, so for an address on a boundary the system's own service map or your water bill is the final word. EPA also notes of its areas served data: "Note: Data on areas served may be incomplete and have not been quality assured."

The Safe Drinking Water Information System is the federal database behind every number here. In EPA's words: "The Safe Drinking Water Act requires states to report drinking water information periodically to EPA. This information is maintained in a federal database, the SDWIS Fed Data Warehouse." We read the public quarterly extract, currently the April to June 2026 edition: 49,378 active community water systems reporting 330 million people served, their counties, sources and listed violations.

EPA's definition of a public water system: "A public water system provides water for human consumption through pipes or other constructed conveyances to at least 15 service connections or serves an average of at least 25 people for at least 60 days a year." A community water system is the subset serving the same people year round, your utility rather than a campground. "The public drinking water systems regulated by EPA and delegated states and tribes provide drinking water to 90 percent of Americans." This site covers community systems only, because they are the ones with customers, counties and Consumer Confidence Reports.

Neither, and the difference between violation categories is most of the story. Health based violations mean a legal limit or required treatment was exceeded or missed; monitoring and reporting violations mean a test or report did not happen on time. EPA is blunt about the database's limits: "Compliance statistics are based on violations reported by states to the EPA Safe Drinking Water Information System (SDWIS). EPA is aware of inaccuracies and underreporting of some data in this system. We are working with the states to improve the quality of the data." And about reading absence as cleanliness: "However, EPA is aware of underreporting of violations and returns to compliance into SDWIS. EPA cautions users that a list of systems with no violations in ECHO represents the best data we have available, but may not be a true representation of current compliance." This site repeats those caveats wherever it shows a count, and issues no verdicts of its own.

Partly water, mostly paperwork. Every violation here was reported by a state primacy agency to EPA, and states differ in how completely and quickly they report: EPA says so itself and works "with the states to improve the quality of the data." A state where 70 percent of systems show a recent health based violation is not necessarily worse than one showing 6 percent; it may simply report more thoroughly. That is why every count here is labelled as EPA listed, and why the comparison worth making is between a state and its own record over time.

By reported population served in the current extract, about 72 percent of community system customers drink treated surface water and 28 percent ground water, but the state mix varies enormously: 9 states (Delaware, Florida, Hawaii, Idaho, Iowa, Louisiana, Minnesota, Mississippi, Wisconsin) serve more people from wells than from rivers and lakes, while Virginia and Colorado are almost entirely surface water. The state pages break the split down county by county.

The annual test result document your water system must send you: "EPA requires community water systems to deliver a Consumer Confidence Report, also known as an annual drinking water quality report, to their customers. These reports provide Americans information about their local drinking water quality." "Reports must be sent by your water supplier each year by July 1." It lists what the system found in the water, in numbers, against EPA's limits, which makes it more informative than any violation summary including ours. EPA runs a search for them, linked from every report this site's tool issues, and your utility's website or billing office has the current one.

Both sit outside state programs. Tribal systems are regulated by EPA regions or the Navajo Nation's own primacy program; the federal file records no usable county for 748 of them, so the ZIP tool may not list a tribal system that serves you, and EPA's tribal drinking water program is the right door. Private wells are not regulated at all: "The quality and safety of drinking water from private domestic wells are not regulated by the Federal Government under the Safe Drinking Water Act nor by most state governments and laws." State and county health departments publish well testing guidance.