Metals
Magnesium in U.S. tap water
111 public water systems across 20 U.S. states report Magnesium 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 | 25–26 mg/L | 2600.0× the limit |
| Burbank, CA 2024 annual report | 14–23 mg/L | 230.0× the limit |
| Vancouver, WA 2024 annual report | 12 mg/L | 1.0× the limit |
Within the federal limit (1)
| Water system | Measured |
|---|---|
| Overland Park, KS 2023 annual report | 12 |
Frequently asked
+What is Magnesium?
A naturally occurring mineral that contributes to water hardness. Not federally regulated for health; affects scaling and taste.
+What is the federal limit for Magnesium in drinking water?
The federal MCL for Magnesium is 0.1 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 Magnesium over the federal limit?
3 of the 111 public water systems on The Water Map report Magnesium at or above its federal limit, spanning 20 U.S. states. The full list is on this page.
+How can I check if Magnesium 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 Magnesium.