Disinfectants
Chlorine in U.S. tap water
705 public water systems across 36 U.S. states report Chlorine in their annual Consumer Confidence Report. 21 sit at or above the federal limit.
What it is
A disinfectant added to drinking water to kill bacteria and viruses.
Why it's regulated
Effective and necessary, but high residual levels can cause taste and odor issues; the EPA caps the residual disinfectant level.
At or above the federal limit (21)
| Water system | Measured | vs. limit |
|---|---|---|
| Pittsburgh, PA 2024 annual report | 104 mg/L | 26.0× the limit |
| Amelano Manor, MD 2024 annual report | 1.4–11 mg/L | 2.8× the limit |
| Santa Fe I.d. — Rancho Santa Fe, Ca, CA 2023 annual report | 0–10 mg/L | 2.5× the limit |
| Glendora-city, Water Dept. — Glendora, Ca, CA 2021 annual report | 0.03–6.4 mg/L | 1.6× the limit |
| Chapel Hill Water System, MD 2024 annual report | 3.54–6 mg/L | 1.5× the limit |
| City of Hampton, VA 2024 annual report | 0–5.4 mg/L | 1.4× the limit |
| City of Newport News, VA 2025 annual report | 0–5.4 mg/L | 1.4× the limit |
| City of Poquoson, VA 2024 annual report | 0–5.4 mg/L | 1.4× the limit |
| City of Poquoson, VA 2025 annual report | 0–5.4 mg/L | 1.4× the limit |
| Hampton, VA 2025 annual report | 0–5.4 mg/L | 1.4× the limit |
| Newport News, VA 2024 annual report | 0–5.4 mg/L | 1.4× the limit |
| York County, VA 2024 annual report | 0–5.4 mg/L | 1.4× the limit |
| York County, VA 2025 annual report | 0–5.4 mg/L | 1.4× the limit |
| Palm Coast, FL 2024 annual report | 0.6–5.1 mg/L | 1.3× the limit |
| Cedarhurst Mhp, MD 2024 annual report | 4 mg/L | 1.0× the limit |
| City of Lighthouse Point, FL 2024 annual report | 0.62–4 mg/L | 1.0× the limit |
| Eden Mobile Home Park, MD 2024 annual report | 4 mg/L | 1.0× the limit |
| Esparto C.s.d. — Esparto, Ca, CA 2023 annual report | 0–4 mg/L | 1.0× the limit |
| Frisco, TX 2024 annual report | 4 mg/L | 1.0× the limit |
| Pompano Beach, FL 2024 annual report | 0.62–4 mg/L | 1.0× the limit |
| Town of Lauderdale-by-the-sea, FL 2024 annual report | 0.62–4 mg/L | 1.0× the limit |
Approaching the limit (19)
| Water system | Measured | vs. limit |
|---|---|---|
| Thornton, CO 2024 annual report | 1.7–3.9 mg/L | 1.0× the limit |
| Morro Bay Pw Dept - Water Division — Morro Bay, Ca, CA 2023 annual report | 0.18–3.84 mg/L | 1.0× the limit |
| Cal-am Water Coronado — Imperial Beach, Ca, CA 2023 annual report | 3.8 mg/L | 0.9× the limit |
| Coral Springs, FL 2024 annual report | 0.8–3.8 mg/L | 0.9× the limit |
| Hialeah, FL 2023 annual report | 3.8 mg/L | 0.9× the limit |
| Huntsville, AL 2024 annual report | 2.1–3.8 mg/L | 0.9× the limit |
| Valencia Heights Water Co. — West Covina, Ca, CA 2020 annual report | 0.04–3.8 mg/L | 0.9× the limit |
| Valencia Heights Water Co. — West Covina, Ca, CA 2022 annual report | 0.3–3.8 mg/L | 0.9× the limit |
| Columbus, GA 2024 annual report | 1.6–3.76 mg/L | 0.9× the limit |
| West Palm Beach, FL 2024 annual report | 0–3.7 mg/L | 0.9× the limit |
| Fort Myers, FL 2024 annual report | 0–3.68 mg/L | 0.9× the limit |
| City of Alhambra — Alhambra, Ca, CA 2023 annual report | 0.01–3.59 mg/L | 0.9× the limit |
| Wichita Falls, TX 2024 annual report | 3–3.56 mg/L | 0.9× the limit |
| Jacksonville, FL 2024 annual report | 0.21–3.5 mg/L | 0.9× the limit |
| Santa Monica-city, Water Division — Los Angeles, Ca, CA 2023 annual report | 0–3.5 mg/L | 0.9× the limit |
| Cary, NC 2025 annual report | 0.37–3.29 mg/L | 0.8× the limit |
| Woodlands Development — Arroyo Grande, Ca, CA 2023 annual report | 0.05–3.29 mg/L | 0.8× the limit |
| Santa Ynez River Water Cons. Dist. Id#1 — Santa Ynez, Ca, CA 2023 annual report | 0.3–3.22 mg/L | 0.8× the limit |
| Solvang Water Division — Solvang, Ca, CA 2023 annual report | 0.3–3.22 mg/L | 0.8× the limit |
Within the federal limit (664)
Showing 50 of 664. The full list is in the JSON API.
Chlorine by state
Every state where a public water system reports Chlorine in its annual report, ranked by systems at or above the federal limit.
Frequently asked
+What is Chlorine?
A disinfectant added to drinking water to kill bacteria and viruses. Effective and necessary, but high residual levels can cause taste and odor issues; the EPA caps the residual disinfectant level.
+What is the federal limit for Chlorine in drinking water?
The federal MCL for Chlorine is 4 mg/L. The EPA enforces this against the regulated reporting statistic (typically a running annual average or 90th percentile), not a single-sample spike.
+How many U.S. water systems have Chlorine over the federal limit?
21 of the 705 public water systems on The Water Map report Chlorine at or above its federal limit, spanning 36 U.S. states. The full list is on this page.
+Which states report the most Chlorine in their drinking water?
Of the systems on The Water Map, Virginia (8 systems at or above the limit), Maryland (4 systems at or above the limit), Florida (4 systems at or above the limit) report the most Chlorine exceedances. The state-by-state table on this page lists every state.
+How can I check if Chlorine is in my city's tap water?
Search your city on The Water Map (https://www.thewatermap.com/) or browse the list on this page. Every U.S. public water utility is required to publish an annual Consumer Confidence Report that lists every contaminant it measured, including Chlorine.