Copper Contamination

Copper in Montana Drinking Water

Ranked by 90th percentile copper level (mg/L) · Data from EPA SDWIS & UCMR

Cities Tested

Exceeds Limit

100%

% Exceeds Limit

1.887 mg/L

State Avg

▼ 0% vs national

vs National

Health Violations

Analysis

Copper in Montana: what the data shows

Montana has 48 cities with copper monitoring data. The state average 90th percentile copper level is 1.887 mg/L, compared to 28.808 mg/L nationally — better than the national average. 48 cities exceed the EPA action level of 1.3 mg/L. Copper in drinking water typically comes from corrosion of copper pipes and plumbing fixtures, particularly in older homes. The EPA action level of 1.3 mg/L is the 90th percentile threshold — if more than 10% of tap samples exceed it, utilities must take corrective action including adjusting water chemistry to reduce corrosivity. Short-term copper exposure above the action level can cause gastrointestinal distress. Long-term exposure at elevated levels is associated with liver and kidney damage. Flushing your tap for 30 seconds before use and using an NSF 53-certified filter can reduce copper exposure.

Comparison

Cities exceeding 1.3 mg/L EPA Action Level

Montana

100%

48 of 48 cities

← = Exactly at national rate

National avg

100%

3953 of 3953 cities

City Map

Copper data across Montana

Each dot is a city, colored by overall water quality grade. Cities with copper levels above the 1.3 mg/L EPA action level are highlighted. Size reflects population served.

Worst Offenders

Top 10 cities by copper level in Montana

Highest Copper levels (mg/L)

All Cities

All Montana cities ranked by copper level

#	City	Level	Exceeds?	Violations	Grade
1	Hamilton	7.110 mg/L	Yes	20	D+
2	Clancy	3.200 mg/L	Yes	68	F
3	Absarokee	2.610 mg/L	Yes	4	B+
4	Ballantine	2.520 mg/L	Yes	8	C+
5	Ballantine	2.520 mg/L	Yes	8	C+
6	Havre	2.440 mg/L	Yes	151	F
7	Great Falls	2.210 mg/L	Yes	64	F
8	Harlem	2.180 mg/L	Yes	237	D
9	Hardin	2.130 mg/L	Yes	6	F
10	Helena	2.100 mg/L	Yes	90	F
11	Poplar	2.030 mg/L	Yes	8	B
12	Dillon	2.020 mg/L	Yes	36	F
13	Medicine Lake	1.930 mg/L	Yes	9	B
14	Laurel	1.920 mg/L	Yes	6	C+
15	Fairview	1.920 mg/L	Yes	4	B+
16	Big Sky	1.890 mg/L	Yes	17	F
17	Missoula	1.870 mg/L	Yes	189	F
18	Kalispell	1.860 mg/L	Yes	162	F
19	Seeley Lake	1.800 mg/L	Yes	6	B+
20	Choteau	1.770 mg/L	Yes	5	B-
21	Box Elder	1.750 mg/L	Yes	21	B-
22	Fort Harrison	1.750 mg/L	Yes	0	B+
23	Eureka	1.720 mg/L	Yes	16	C-
24	Browning	1.700 mg/L	Yes	40	F
25	Philipsburg	1.700 mg/L	Yes	19	F
26	Lame Deer	1.650 mg/L	Yes	54	F
27	Conrad	1.645 mg/L	Yes	29	D
28	Fort Benton	1.610 mg/L	Yes	1	B+
29	Polson	1.560 mg/L	Yes	26	D+
30	Huntley	1.560 mg/L	Yes	2	B+
31	Billings	1.550 mg/L	Yes	51	F
32	Butte	1.500 mg/L	Yes	4	B+
33	Frenchtown	1.500 mg/L	Yes	28	C+
34	Bigfork	1.490 mg/L	Yes	20	A-
35	Big Timber	1.490 mg/L	Yes	6	B+
36	Plains	1.490 mg/L	Yes	0	B+
37	Malta	1.480 mg/L	Yes	0	D
38	Belgrade	1.465 mg/L	Yes	27	F
39	Bozeman	1.440 mg/L	Yes	57	F
40	Sidney	1.400 mg/L	Yes	27	F
41	Libby	1.400 mg/L	Yes	50	F
42	Columbus	1.400 mg/L	Yes	8	D
43	Boulder	1.400 mg/L	Yes	6	B+
44	Corwin Springs	1.400 mg/L	Yes	18	C+
45	Stevensville	1.390 mg/L	Yes	13	B-
46	Darby	1.390 mg/L	Yes	26	C
47	Plentywood	1.360 mg/L	Yes	0	B+
48	Culbertson	1.350 mg/L	Yes	6	B+

FAQ

Frequently asked questions about copper in Montana

Is copper in Montana drinking water safe?

48 cities in Montana exceed the EPA action level of 1.3 mg/L for copper. The state average is 1.887 mg/L. Copper levels are highest in homes with copper plumbing, particularly when water sits in pipes overnight. Flushing the tap before use significantly reduces copper in drinking water.

What causes high copper levels in Montana tap water?

Copper typically leaches from copper pipes and brass fittings within homes, not from the water source itself. Corrosive (low pH or soft) water accelerates this leaching. Water utilities with high copper readings are required to adjust water chemistry to reduce corrosivity. You can reduce exposure by flushing your tap for 30 seconds before use.

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