Metals
Calcium in U.S. tap water
117 public water systems across 22 U.S. states report Calcium in their annual Consumer Confidence Report. 3 sit at or above the federal limit.
What it is
A naturally occurring mineral that contributes to water hardness.
Why it's regulated
Not federally regulated for health; affects scaling and taste.
At or above the federal limit (3)
| Water system | Measured | vs. limit |
|---|---|---|
| Pomona, CA 2024 annual report | 49–76 mg/L | 760.0× the limit |
| Burbank, CA 2024 annual report | 38–84 mg/L | 84.0× the limit |
| Vancouver, WA 2024 annual report | 37 mg/L | 1.0× the limit |
Frequently asked
+What is Calcium?
A naturally occurring mineral that contributes to water hardness. Not federally regulated for health; affects scaling and taste.
+What is the federal limit for Calcium in drinking water?
The federal MCL for Calcium is 1 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 Calcium over the federal limit?
3 of the 117 public water systems on The Water Map report Calcium at or above its federal limit, spanning 22 U.S. states. The full list is on this page.
+How can I check if Calcium 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 Calcium.