Editorial standards

Tap Water Results is a small, independent publication, and we don't publish staff names. We'd rather you didn't have to trust us at all: every number on this site comes from a public U.S. EPA record, every page links to that record, and this page explains exactly how we handle the data.

Where the numbers come from

• Only official data. Results, limits and violations come from EPA's Safe Drinking Water Information System and EPA's Unregulated Contaminant Monitoring Rule data. Health statements and limits come from EPA's regulations. Each contaminant page lists its sources.
• We don't change reported numbers. We convert units and compare results to the limits the way EPA does. We never adjust, estimate or fill in a value.
• Gaps are shown, not hidden. "No results" is never presented as "safe". Systems EPA didn't test for PFAS are labelled as not tested, and lead results more than five years old are labelled out of date.
• A few details are collected by hand, and labelled. Links to utilities' own water quality reports, what utilities say they are doing about PFAS, state PFAS limits and lead service line counts come from utility and state websites, not EPA. Each one shows its source and the date we checked it. Every quarter we recheck every link automatically, hide any that have disappeared, and flag statements more than a year old for a fresh look.
• Every page can be checked. Each utility page links to EPA's own report for that system and to the files we used, under "Check these numbers yourself".

How we check the data

Pages are built automatically from EPA's files by our own code, so the same rules apply to every system. Before a release is published:

• Our PFAS comparisons are reconciled with EPA's. We recount how many systems are above each 2024 PFAS limit and compare the totals with the counts EPA published in its UCMR 5 data summary. The release doesn't go out if any count is off by more than 2%.
• The calculations are tested. Unit conversions, limit comparisons, averaging and the matching of ZIP codes and cities to water systems are covered by automated tests that must pass.
• Impossible values are screened out. EPA's database contains some obvious entry errors (one lead result is recorded as 30 million ppb). Results far beyond anything physically plausible are labelled on the page and left out of summaries, counts and rankings.
• Out-of-date results stay out of the rankings. State counts and national tables use lead results from the last five years only, and older ones are counted separately.

How we write

• Plain language first, with the regulatory term in brackets when you'll need it to talk to your utility.
• We say what a result does and doesn't mean. Utility data can't show lead from your own pipes, "not detected" means below EPA's reporting limit, and a PFAS result above the 2024 limit isn't a violation until 2029.
• This site reports monitoring and regulatory data. It isn't medical advice, and we point to your doctor, utility or state program where they're the right source.

Money and independence

• No utility, agency or company can pay to be listed, ranked, hidden or described differently.
• No ads and no affiliate links. Where a page mentions filters, it names the certification to look for (for example NSF/ANSI 53 or 58 for PFAS), not a brand.
• We don't remove accurate results at anyone's request.

Corrections and updates

EPA updates its drinking water data quarterly and we rebuild every page when it does. The current release uses EPA's 2026Q3 data (Oct 13, 2026) and the final UCMR 5 file (Oct 15, 2026). If something looks wrong, email support@tapwaterresults.com. Our corrections policy explains what happens next. Full method and caveats.