Copper Contamination

Copper in Connecticut Drinking Water

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

Cities Tested

Exceeds Limit

100%

% Exceeds Limit

1.880 mg/L

State Avg

▼ 0% vs national

vs National

105

Health Violations

Analysis

Copper in Connecticut: what the data shows

Connecticut has 41 cities with copper monitoring data. The state average 90th percentile copper level is 1.880 mg/L, compared to 29.400 mg/L nationally — better than the national average. 41 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

Connecticut

100%

41 of 41 cities

← = Exactly at national rate

National avg

100%

3810 of 3810 cities

City Map

Copper data across Connecticut

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 Connecticut

Highest Copper levels (mg/L)

All Cities

All Connecticut cities ranked by copper level

#	City	Level	Exceeds?	Violations	Grade
1	Putnam	3.300 mg/L	Yes	19	D
2	Woodstock	3.300 mg/L	Yes	120	F
3	Waterford	3.240 mg/L	Yes	16	C-
4	Carroll	2.950 mg/L	Yes	9	C
5	Carroll	2.950 mg/L	Yes	10	C
6	Old Lyme	2.810 mg/L	Yes	42	D
7	Hebron	2.700 mg/L	Yes	21	F
8	Kent	2.370 mg/L	Yes	30	D
9	North Stonington	2.260 mg/L	Yes	19	C
10	Montville	2.140 mg/L	Yes	143	F
11	Tolland	2.130 mg/L	Yes	24	F
12	Willington	1.920 mg/L	Yes	41	F
13	Sharon	1.900 mg/L	Yes	9	F
14	Brooklyn	1.800 mg/L	Yes	14	C-
15	Killingly	1.800 mg/L	Yes	32	F
16	Ledyard	1.800 mg/L	Yes	23	D+
17	Harwinton	1.740 mg/L	Yes	5	D
18	New Milford	1.730 mg/L	Yes	85	F
19	East Hampton	1.700 mg/L	Yes	64	D
20	Barkhamsted	1.650 mg/L	Yes	12	C
21	Stonington	1.610 mg/L	Yes	6	B
22	Cheshire	1.590 mg/L	Yes	28	F
23	Southington	1.590 mg/L	Yes	12	F
24	Wolcott	1.590 mg/L	Yes	18	F
25	Danbury	1.510 mg/L	Yes	59	F
26	Lisbon	1.500 mg/L	Yes	27	F
27	Deep River	1.500 mg/L	Yes	5	C
28	Washington	1.500 mg/L	Yes	31	F
29	Farmington	1.480 mg/L	Yes	3	D+
30	Avon	1.480 mg/L	Yes	3	C+
31	Oxford	1.470 mg/L	Yes	6	B
32	Preston	1.460 mg/L	Yes	23	D+
33	Mansfield	1.440 mg/L	Yes	85	F
34	Griswold	1.440 mg/L	Yes	53	F
35	Newtown	1.440 mg/L	Yes	46	F
36	Manchester	1.400 mg/L	Yes	8	C
37	Clinton	1.400 mg/L	Yes	4	D+
38	Greenwich	1.396 mg/L	Yes	5	F
39	Plainfield	1.370 mg/L	Yes	37	D
40	Hampton	1.360 mg/L	Yes	1	B
41	Watertown	1.350 mg/L	Yes	11	D+

FAQ

Frequently asked questions about copper in Connecticut

Is copper in Connecticut drinking water safe?

41 cities in Connecticut exceed the EPA action level of 1.3 mg/L for copper. The state average is 1.880 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 Connecticut 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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