Copper Contamination

Copper in Wisconsin Drinking Water

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

Cities Tested

Exceeds Limit

100%

% Exceeds Limit

1.980 mg/L

State Avg

▼ 0% vs national

vs National

388

Health Violations

Analysis

Copper in Wisconsin: what the data shows

Wisconsin has 99 cities with copper monitoring data. The state average 90th percentile copper level is 1.980 mg/L, compared to 28.808 mg/L nationally — better than the national average. 99 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

Wisconsin

100%

99 of 99 cities

← = Exactly at national rate

National avg

100%

3953 of 3953 cities

City Map

Copper data across Wisconsin

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 Wisconsin

Highest Copper levels (mg/L)

All Cities

All Wisconsin cities ranked by copper level

#	City	Level	Exceeds?	Violations	Grade
1	Spring Green	12.825 mg/L	Yes	14	C
2	Ixonia	7.760 mg/L	Yes	16	D+
3	Elm Grove	4.400 mg/L	Yes	28	F
4	Osseo	4.230 mg/L	Yes	1	A
5	Chetek	4.210 mg/L	Yes	6	C+
6	Altoona	4.100 mg/L	Yes	15	C+
7	Columbus	3.062 mg/L	Yes	8	B
8	Cuba City	2.800 mg/L	Yes	4	B
9	Sparta	2.430 mg/L	Yes	2	B
10	Park Falls	2.390 mg/L	Yes	1	A-
11	Hayward	2.370 mg/L	Yes	19	F
12	Genoa City	2.350 mg/L	Yes	15	B-
13	Appleton	2.250 mg/L	Yes	4	B+
14	Strum	2.200 mg/L	Yes	5	B+
15	Bristol	2.100 mg/L	Yes	10	B
16	Colby	2.100 mg/L	Yes	0	A-
17	Lake Geneva	2.075 mg/L	Yes	24	C
18	Plymouth	2.050 mg/L	Yes	8	C+
19	Seymour	2.000 mg/L	Yes	2	A-
20	Minocqua	2.000 mg/L	Yes	4	C-
21	Clayton	2.000 mg/L	Yes	1	B-
22	Thorp	1.980 mg/L	Yes	3	D+
23	De Pere	1.950 mg/L	Yes	38	B
24	Blair	1.940 mg/L	Yes	2	A-
25	Manawa	1.900 mg/L	Yes	2	B
26	Luck	1.900 mg/L	Yes	1	A-
27	Abbotsford	1.860 mg/L	Yes	2	B
28	Menasha	1.852 mg/L	Yes	1	B+
29	Hobart	1.840 mg/L	Yes	2	B-
30	Deerfield	1.840 mg/L	Yes	7	B
31	Waldo	1.811 mg/L	Yes	1	A-
32	Menomonie	1.800 mg/L	Yes	30	F
33	Cedarburg	1.800 mg/L	Yes	1	B+
34	Barron	1.800 mg/L	Yes	1	B+
35	Sherwood	1.800 mg/L	Yes	12	B-
36	Owen	1.800 mg/L	Yes	5	C-
37	Laona	1.800 mg/L	Yes	19	D+
38	Elk Mound	1.800 mg/L	Yes	4	B+
39	Colfax	1.780 mg/L	Yes	2	B
40	Black River Falls	1.762 mg/L	Yes	11	D+
41	Wisconsin Dells	1.750 mg/L	Yes	18	F
42	Camp Douglas	1.750 mg/L	Yes	4	B
43	Edgar	1.740 mg/L	Yes	1	B+
44	Adell	1.740 mg/L	Yes	1	A-
45	Footville	1.731 mg/L	Yes	1	A-
46	Chippewa Falls	1.710 mg/L	Yes	12	D+
47	Marinette	1.700 mg/L	Yes	0	A-
48	Slinger	1.700 mg/L	Yes	2	B
49	Warrens	1.700 mg/L	Yes	6	A-
50	Manitowoc	1.660 mg/L	Yes	0	B+
51	Pittsville	1.640 mg/L	Yes	1	A-
52	Merrillan	1.610 mg/L	Yes	1	B+
53	Madison	1.600 mg/L	Yes	14	F
54	Lake Mills	1.600 mg/L	Yes	11	C+
55	Lac Du Flambeau	1.600 mg/L	Yes	1	A
56	West Baraboo	1.580 mg/L	Yes	0	A-
57	Wrightstown	1.570 mg/L	Yes	4	B
58	Withee	1.560 mg/L	Yes	0	A
59	Fox Lake	1.550 mg/L	Yes	6	B
60	Brookfield	1.540 mg/L	Yes	32	C-
61	Hortonville	1.534 mg/L	Yes	1	B+
62	Onalaska	1.530 mg/L	Yes	2	A-
63	Cascade	1.530 mg/L	Yes	1	B+
64	Reedsburg	1.520 mg/L	Yes	1	B+
65	Sturgeon Bay	1.520 mg/L	Yes	8	B+
66	West Salem	1.505 mg/L	Yes	3	B+
67	Twin Lakes	1.502 mg/L	Yes	29	F
68	Eau Claire	1.500 mg/L	Yes	18	D+
69	Mequon	1.500 mg/L	Yes	21	F
70	Baraboo	1.500 mg/L	Yes	0	B
71	Denmark	1.500 mg/L	Yes	4	B
72	Cameron	1.500 mg/L	Yes	10	B+
73	Fond Du Lac	1.484 mg/L	Yes	51	F
74	West Bend	1.460 mg/L	Yes	11	F
75	Elkhorn	1.460 mg/L	Yes	19	F
76	Oconomowoc	1.450 mg/L	Yes	13	B
77	Hillsboro	1.450 mg/L	Yes	13	C+
78	Rice Lake	1.440 mg/L	Yes	17	F
79	Delavan	1.430 mg/L	Yes	6	F
80	Pulaski	1.425 mg/L	Yes	0	A-
81	Mauston	1.420 mg/L	Yes	17	F
82	Winneconne	1.410 mg/L	Yes	17	C
83	Loyal	1.410 mg/L	Yes	2	A-
84	Green Bay	1.400 mg/L	Yes	74	D+
85	Fort Mccoy	1.400 mg/L	Yes	4	B+
86	Ashland	1.400 mg/L	Yes	14	D+
87	Waupaca	1.400 mg/L	Yes	3	B-
88	Mosinee	1.400 mg/L	Yes	15	F
89	Ladysmith	1.400 mg/L	Yes	18	D
90	Mondovi	1.400 mg/L	Yes	5	B+
91	North Freedom	1.400 mg/L	Yes	3	B+
92	Stetsonville	1.400 mg/L	Yes	6	C+
93	Watertown	1.390 mg/L	Yes	10	D
94	Elroy	1.390 mg/L	Yes	5	A-
95	Hazel Green	1.390 mg/L	Yes	14	F
96	Dorchester	1.390 mg/L	Yes	1	B+
97	Reeseville	1.390 mg/L	Yes	3	B-
98	Reedsville	1.370 mg/L	Yes	5	B+
99	Mishicot	1.360 mg/L	Yes	0	B+

FAQ

Frequently asked questions about copper in Wisconsin

Is copper in Wisconsin drinking water safe?

99 cities in Wisconsin exceed the EPA action level of 1.3 mg/L for copper. The state average is 1.980 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 Wisconsin 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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