Tap Water Results

Data sources and method

Everything on this site comes from public U.S. EPA data. We don't collect samples, and we don't change the numbers systems reported. This page explains what each number means and where it can mislead.

Sources

Which systems are included

Active community water systems: those that serve the same people year-round (cities, towns, water districts, mobile home parks). Schools, campgrounds and restaurants with their own wells are not included.

PFAS: how results are compared to the limits

We follow EPA's own method from its July 2026 UCMR 5 Data Summary:

Checked against EPA: applying this to every system in the file reproduces EPA's published counts of systems above each limit (EPA Table 4) exactly.

This is not compliance. The PFAS limits take effect in 2029 (EPA has proposed 2031 for PFOA and PFOS, and proposed rescinding the PFHxS, PFNA, GenX and Hazard Index limits, but neither proposal is final as of Nov 15, 2026). Compliance will be judged on running annual averages of compliance monitoring, not on UCMR 5.

Not tested vs. not detected

"Not detected" means EPA's labs looked and found nothing above the reporting limit (about 2 to 20 ppt for most PFAS). "Not tested" means the system wasn't in the sample. Most systems serving fewer than 3,300 people were not tested, and we say so on their pages.

Lead and copper

Systems sample taps in homes most likely to have lead (lead service lines first) and report the 90th percentile. We show the most recent period and history. The action level is 15 ppb. Under the Lead and Copper Rule Improvements it becomes 10 ppb on November 1, 2027. The 90th percentile is not your home's level.

Violations

From SDWIS, counted once per violation, from January 2016 on for the detail tables. Health-based means a limit was exceeded (MCL), a required treatment step was missed (treatment technique) or a disinfectant level was exceeded. Monitoring and reporting violations mean required tests or reports were missing or late. Routine compliance sample results for regulated contaminants such as nitrate and arsenic are held by states and are not in EPA's national download, so for those contaminants we report violations rather than levels. Your utility's annual Consumer Confidence Report lists them.

Matching ZIP codes and cities to water systems

Water systems don't follow ZIP code lines. We match in this order and label each match:

  1. Reported: ZIP codes the system itself reported serving, in UCMR 3, 4 or 5 or in SDWIS.
  2. City: the cities and towns a system lists as served, matched by name to 2020 Census places and towns, then to the ZIP areas that overlap them.
  3. Mailing address: for small systems with neither, the ZIP of the system's mailing address. This is the weakest match.

When more than one system may serve a ZIP or city, we list them all, largest first, and say so. Your water bill names your system.

Health guidelines

Legal limits (MCLs) and health goals (MCLGs) are EPA's. For contaminants without a limit we show the reference value EPA uses in its UCMR data summaries (for example EPA's 10 ppb health reference level for lithium, USGS screening levels for PFBA and PFHxA). Some states set stricter limits, so check your state's drinking water program. Nothing here is medical advice.

Updates

We rebuild when EPA publishes a new quarterly SDWIS release. This build: Nov 15, 2026.

Corrections

If a system's details look wrong, the error is usually in what was reported to EPA, and your state drinking water program can correct it. If we've made a matching or calculation error, tell us via the About page.