Copper Contamination

Copper in California Drinking Water

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

168

Cities Tested

168

Exceeds Limit

100%

% Exceeds Limit

10.522 mg/L

State Avg

▼ 0% vs national

vs National

620

Health Violations

Analysis

Copper in California: what the data shows

California has 168 cities with copper monitoring data. The state average 90th percentile copper level is 10.522 mg/L, compared to 29.400 mg/L nationally — better than the national average. 168 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

California

100%

168 of 168 cities

← = Exactly at national rate

National avg

100%

3810 of 3810 cities

City Map

Copper data across California

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 California

Highest Copper levels (mg/L)

All Cities

All California cities ranked by copper level

#	City	Level	Exceeds?	Violations	Grade
1	Dixon	310.000 mg/L	Yes	2	A
2	Thousand Oaks	287.000 mg/L	Yes	1	A
3	Angels Camp	225.000 mg/L	Yes	21	B+
4	Julian	177.000 mg/L	Yes	22	D
5	Redding	111.900 mg/L	Yes	49	F
6	Antioch	104.000 mg/L	Yes	3	A
7	Gonzales	88.400 mg/L	Yes	53	F
8	West Covina	75.000 mg/L	Yes	25	F
9	Corona Del Mar	50.000 mg/L	Yes	3	C-
10	Yucaipa	30.000 mg/L	Yes	9	C+
11	Fort Bragg	8.600 mg/L	Yes	4	B
12	Carmel Valley	6.320 mg/L	Yes	45	C+
13	La Puente	5.600 mg/L	Yes	1	B+
14	Mariposa	5.100 mg/L	Yes	71	C
15	Fresno	4.600 mg/L	Yes	523	F
16	Santa Rosa	4.190 mg/L	Yes	177	F
17	Altoona	4.100 mg/L	Yes	3	B
18	Palo Verde	4.050 mg/L	Yes	7	C
19	San Andreas	3.730 mg/L	Yes	17	B-
20	Lakehead	3.650 mg/L	Yes	4	B
21	Shaver Lake	3.500 mg/L	Yes	0	B+
22	Rio Dell	3.400 mg/L	Yes	3	A
23	Fairfield	3.150 mg/L	Yes	7	B-
24	Beverly Hills	3.040 mg/L	Yes	18	B
25	Cobb	2.900 mg/L	Yes	3	C+
26	Smith River	2.850 mg/L	Yes	11	C+
27	Clearlake Oak	2.800 mg/L	Yes	4	B+
28	Morro Bay	2.600 mg/L	Yes	12	A-
29	Cloverdale	2.600 mg/L	Yes	9	B
30	Montara	2.600 mg/L	Yes	3	A-
31	Roseville	2.544 mg/L	Yes	11	B
32	Portola	2.500 mg/L	Yes	71	C-
33	Eldorado Hills	2.500 mg/L	Yes	8	B
34	Barona North Reservation	2.345 mg/L	Yes	0	A-
35	Solvang	2.320 mg/L	Yes	6	B
36	Porterville	2.230 mg/L	Yes	74	F
37	Villa Park	2.215 mg/L	Yes	1	A-
38	Cedarpines Park	2.200 mg/L	Yes	5	A
39	Clovis	2.170 mg/L	Yes	221	F
40	Pauma Valley	2.160 mg/L	Yes	88	F
41	Petaluma	2.130 mg/L	Yes	2	B
42	Sutter Creek	2.110 mg/L	Yes	7	B+
43	Salinas	2.105 mg/L	Yes	639	F
44	Blythe	2.100 mg/L	Yes	143	D
45	Jamestown	2.100 mg/L	Yes	25	C+
46	La Grange	2.042 mg/L	Yes	13	B
47	Point Reyes Station	2.000 mg/L	Yes	0	A-
48	Olympic Valley	2.000 mg/L	Yes	1	B+
49	Mt. Shasta	1.965 mg/L	Yes	20	B
50	Los Alamos	1.960 mg/L	Yes	0	A
51	Novato	1.950 mg/L	Yes	3	B+
52	Oak View	1.935 mg/L	Yes	12	B+
53	Cambria	1.930 mg/L	Yes	4	A-
54	Los Gatos	1.925 mg/L	Yes	138	D
55	San Jacinto	1.900 mg/L	Yes	9	B
56	Chico	1.850 mg/L	Yes	306	F
57	Hollister	1.847 mg/L	Yes	132	F
58	Willits	1.845 mg/L	Yes	23	C-
59	Fremont	1.800 mg/L	Yes	3	B-
60	San Bernardino	1.800 mg/L	Yes	192	F
61	Santa Cruz	1.800 mg/L	Yes	38	F
62	San Luis Obispo	1.800 mg/L	Yes	27	F
63	Valley Center	1.800 mg/L	Yes	15	F
64	El Verano	1.800 mg/L	Yes	0	B+
65	Idyllwild	1.800 mg/L	Yes	10	B
66	La Honda	1.800 mg/L	Yes	9	C-
67	Carmel	1.796 mg/L	Yes	49	C-
68	Frazier Park	1.780 mg/L	Yes	56	C+
69	Corona	1.770 mg/L	Yes	81	D
70	La Crescenta	1.760 mg/L	Yes	3	B+
71	Santa Paula	1.760 mg/L	Yes	5	A-
72	Twin Peaks	1.760 mg/L	Yes	3	B
73	Oakland	1.750 mg/L	Yes	13	B
74	Kelseyville	1.750 mg/L	Yes	36	B-
75	Victorville	1.745 mg/L	Yes	1	B+
76	Green Valley Lake	1.730 mg/L	Yes	2	C+
77	Napa	1.700 mg/L	Yes	53	F
78	Watsonville	1.700 mg/L	Yes	74	F
79	Lompoc	1.700 mg/L	Yes	18	C
80	Tahoe City	1.700 mg/L	Yes	11	B+
81	King George	1.700 mg/L	Yes	30	D+
82	Healdsburg	1.700 mg/L	Yes	12	B+
83	Pinecrest	1.700 mg/L	Yes	3	B-
84	Sea Ranch	1.700 mg/L	Yes	4	B
85	Trinity Center	1.667 mg/L	Yes	13	C
86	Lemoore	1.650 mg/L	Yes	112	D
87	Atascadero	1.640 mg/L	Yes	1	B
88	Oceano	1.620 mg/L	Yes	1	A
89	Weed	1.620 mg/L	Yes	12	B-
90	Dunsmuir	1.620 mg/L	Yes	7	B-
91	Alpaugh	1.616 mg/L	Yes	48	B
92	Avalon	1.610 mg/L	Yes	1	A-
93	Nevada City	1.610 mg/L	Yes	8	B+
94	Gilroy	1.609 mg/L	Yes	28	C+
95	Burlingame	1.602 mg/L	Yes	14	A-
96	Pacific Grove	1.600 mg/L	Yes	15	B-
97	Redwood City	1.600 mg/L	Yes	10	B+
98	Port Hueneme	1.600 mg/L	Yes	0	B+
99	Crestline	1.600 mg/L	Yes	9	C+
100	Brooks	1.600 mg/L	Yes	2	B+
101	Cotati	1.600 mg/L	Yes	9	A-
102	Inyokern	1.600 mg/L	Yes	21	D
103	Klamath	1.600 mg/L	Yes	102	D
104	Stinson Beach	1.600 mg/L	Yes	2	A-
105	Clayton	1.597 mg/L	Yes	5	A-
106	San Jose	1.593 mg/L	Yes	142	F
107	Adelanto	1.589 mg/L	Yes	13	C
108	Three Rivers	1.560 mg/L	Yes	177	F
109	Crescent City	1.550 mg/L	Yes	14	C
110	Trinidad	1.550 mg/L	Yes	30	D
111	Pleasanton	1.542 mg/L	Yes	3	B-
112	Bakersfield	1.539 mg/L	Yes	690	F
113	Twain Harte	1.531 mg/L	Yes	5	C+
114	El Cajon	1.530 mg/L	Yes	24	B+
115	St. Helena	1.521 mg/L	Yes	29	C+
116	Avila Beach	1.520 mg/L	Yes	2	A-
117	Mount Shasta	1.510 mg/L	Yes	11	B+
118	Hawthorne	1.505 mg/L	Yes	3	B
119	Stockton	1.505 mg/L	Yes	261	F
120	Ukiah	1.500 mg/L	Yes	14	C+
121	Arcata	1.500 mg/L	Yes	3	A
122	Lakeport	1.500 mg/L	Yes	14	C-
123	Needles	1.500 mg/L	Yes	45	F
124	Nipomo	1.500 mg/L	Yes	1	A
125	Sonoma	1.500 mg/L	Yes	5	B-
126	Sebastopol	1.500 mg/L	Yes	18	B-
127	Bethel Island	1.500 mg/L	Yes	12	C+
128	Point Arena	1.500 mg/L	Yes	24	D
129	South Lake Tahoe	1.490 mg/L	Yes	15	C
130	Rosemead	1.480 mg/L	Yes	17	C-
131	Bridgeport	1.480 mg/L	Yes	47	B-
132	Los Osos	1.470 mg/L	Yes	0	B+
133	Buellton	1.465 mg/L	Yes	2	B+
134	Lancaster	1.455 mg/L	Yes	204	D
135	Campo	1.454 mg/L	Yes	74	D
136	Sacramento	1.453 mg/L	Yes	425	F
137	Santa Barbara	1.450 mg/L	Yes	52	F
138	Camp Pendleton	1.440 mg/L	Yes	13	B
139	Dillon Beach	1.440 mg/L	Yes	32	B
140	Pala	1.438 mg/L	Yes	30	C-
141	Coalinga	1.430 mg/L	Yes	267	D
142	Royal Oaks	1.430 mg/L	Yes	201	D
143	Shingletown	1.420 mg/L	Yes	2	B+
144	Georgetown	1.413 mg/L	Yes	4	B+
145	Spring Valley	1.400 mg/L	Yes	4	B
146	Pomona	1.400 mg/L	Yes	6	C+
147	Eureka	1.400 mg/L	Yes	3	A-
148	Big Bear Lake	1.400 mg/L	Yes	1	B+
149	Point Mugu	1.400 mg/L	Yes	11	A-
150	Grover Beach	1.400 mg/L	Yes	34	F
151	Scotts Valley	1.400 mg/L	Yes	11	B-
152	Fortuna	1.400 mg/L	Yes	7	B-
153	Ojai	1.400 mg/L	Yes	35	C-
154	Mendota	1.400 mg/L	Yes	3	A
155	Mammoth Lakes	1.400 mg/L	Yes	24	B
156	Tahoe Vista	1.400 mg/L	Yes	7	A-
157	Yountville	1.400 mg/L	Yes	4	A-
158	Talmage	1.400 mg/L	Yes	2	B-
159	Loleta	1.400 mg/L	Yes	3	B-
160	Yosemite Np	1.400 mg/L	Yes	10	B-
161	Plymouth	1.400 mg/L	Yes	6	B
162	Bodega Bay	1.400 mg/L	Yes	2	A-
163	San Diego	1.390 mg/L	Yes	43	F
164	Lake Arrowhead	1.390 mg/L	Yes	0	A-
165	Kernville	1.390 mg/L	Yes	38	B-
166	Rosamond	1.380 mg/L	Yes	205	F
167	Forestville	1.376 mg/L	Yes	14	B-
168	Oxnard	1.350 mg/L	Yes	49	F

FAQ

Frequently asked questions about copper in California

Is copper in California drinking water safe?

168 cities in California exceed the EPA action level of 1.3 mg/L for copper. The state average is 10.522 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 California 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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