Disinfection byproducts
Chlorate in U.S. tap water
103 public water systems across 3 U.S. states report Chlorate in their annual Consumer Confidence Report. None currently sit at or above the federal limit.
What it is
A byproduct that can form during disinfection, especially when hypochlorite solutions degrade.
Why it's regulated
Has no enforceable federal limit but is on the EPA contaminant candidate list; high levels can affect the thyroid.
Frequently asked
+What is Chlorate?
A byproduct that can form during disinfection, especially when hypochlorite solutions degrade. Has no enforceable federal limit but is on the EPA contaminant candidate list; high levels can affect the thyroid.
+What is the federal limit for Chlorate in drinking water?
The federal NL for Chlorate is 800 ug/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 Chlorate over the federal limit?
Zero of the 103 public water systems in The Water Map dataset currently report Chlorate at or above its federal limit.
+How can I check if Chlorate 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 Chlorate.