DATA-BACKED RANKINGS
Water quality rankings hub
Rankings use different lenses: Water Safety Score (city exposure profile), PFAS UCMR5 (monitoring), state % at risk (geography), and ZIP compliance (live SDWIS on the homepage). Pick the list that matches your question.
OVERALL CITY SCORES
0–88 composite · UCMR5 + profiles
20 worst cities (Water Safety Score)
Lowest exposure-profile scores among tracked metros — regulatory PFAS and contaminant flags.
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Highest safety scores
10 best cities for tap water
Tracked cities with the fewest UCMR5 MCL flags and lighter contaminant profiles.
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PFAS
EPA UCMR5 · regulated violations
Top 10 systems over PFAS MCL
Highest regulated PFAS above federal limits — compound-by-compound ppt.
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MCL cities + unregulated peaks
Worst cities for PFAS
City guides with MCL violations and highest 6:2 FTS–style peaks.
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UCMR5 · PFOA MCL
Cities where PFOA hit the 4 ppt EPA limit
Sugar Land at the line, Philadelphia at 235 ppt — tracked metros with PFOA ≥ 4 ppt.
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All detections
Top 50 peak PFAS readings
Largest aggregate PFAS across public water systems in UCMR5.
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Editorial · 2026
Top 10 PFAS cities (blog)
Sugar Land 672 ppt 6:2 FTS and links to every city report.
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LEAD, DBPS & VIOLATIONS
Lead service lines · profiles
Top 25 lead pipe risk cities
Cities flagging lead or LSL risk — sorted by Water Safety Score.
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Chlorine · chloramine · DBPs
Top THM / disinfection byproduct risk
Cities with THM, HAA, or DBP called out in structured profiles.
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SDWIS compliance
Top 25 EPA violation records
Cities with the worst Safe Drinking Water Act violation history.
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HARDNESS & CHEMISTRY
STATES & GEOGRAPHY
STAY INFORMED
Weekly rankings & violation alerts
PFAS MCL changes, new violations, and safety-score updates — one email per week.
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METHODOLOGY
PFAS-over-MCL lists cite exact UCMR5 values. Lead and THM lists reflect structured city profiles unless noted. Safety Score is a composite on each city page — not the same as your ZIP's live EPA grade.
How we source and interpret data →