Water System Rankings
Ranked views of EPA SDWIS compliance data and UCMR5 PFAS test results across all 50 states and territories. Each ranking pulls live from the database, refreshed when EPA publishes new SDWIS quarterly extracts or UCMR5 batches. See our methodology.
Most violations
Top 100 water systems ranked by total recorded drinking water violations across all categories tracked by EPA SDWIS.
View ranking →PFAS detection by state
States ranked by share of public water systems where at least one PFAS analyte was detected during UCMR5 testing. EPA Health Advisory limit context included.
View ranking →Browse by US state
Every US state has its own drinking-water profile, click through for the per-state violation history, PFAS occurrence summary, and links to the public water systems serving that state.
How PlainWater rankings are compiled
Every ranking is computed directly from the EPA Safe Drinking Water Information System (SDWIS) or the EPA Fifth Unregulated Contaminant Monitoring Rule (UCMR5) dataset, never editorially curated and never blended with proprietary signals. Each ranked view links to the underlying public water system records so visitors can verify the numbers against the upstream agency.
What rankings mean (and what they do not)
A ranking is a useful navigation lens, it tells you where to start looking, but it is not a judgment about water utility quality, safety, or reputation. A high violation count typically reflects scale and reporting transparency: large utilities serving more people have more sample points and more opportunities for a single failed test to be recorded. A small rural utility with only a handful of customers can have zero recorded violations purely because the testing surface is smaller. We surface raw counts alongside the population served so visitors can sanity-check whether a number reflects systemic risk or just system size.
Why we publish these rankings
Drinking water compliance data is statutorily public under the Safe Drinking Water Act, and EPA already publishes the underlying records. PlainWater makes the rankings navigable so residents can quickly find the systems they depend on, check the recent compliance history, and click through to the official EPA Enforcement and Compliance History Online (ECHO) listing for verification. This is a long-established practice in civic data journalism; we are careful to surface the raw numbers, link to the EPA source, and avoid editorial spin.
Methodology and corrections
Most-violations ranks each public water system (PWSID) by the sum of recorded violations across all categories, Maximum Contaminant Level (MCL), Monitoring & Reporting (M&R), Public Notification, and Other. Health-based violations (the subset most directly relevant to safety) are surfaced separately. PFAS detection groups by state, divides PFAS-detected systems by total tested systems, and surfaces the detection rate. If you find a ranking that you believe is miscomputed, or a record that is misclassified, please contact us with the specific PWSID and the expected correction.
Sources
Every figure on PlainWater is rendered directly from EPA SDWIS drinking-water data, no number is typed in by an editor. This page draws directly on EPA SDWIS data, no figure is typed in by an editor. See our editorial standards & corrections policy, the methodology behind these numbers, or report a data error.