Copper in well water
The county where Copper is found above the limit most often is Coos County, New Hampshire: 15% of 346 private wells tested, according to NH DHHS.
Copper leaches from pipes when water is acidic. Above 1.3 mg/L it causes stomach upset, and long-term exposure can harm the liver and kidneys. Blue-green stains on fixtures are the giveaway.
- EPA limit
- 1.3 mg/L (EPA action level (40 CFR 141.80))
- Nuisance level
- 1 mg/L
- New Hampshire level
- 1.3 mg/L
- CAS number
- 7440-50-8
Where copper is worst, by homeowner tests
Counties ranked by the share of private wells above the state guidance level in tests homeowners sent to the state lab. Shares combine town summaries, weighted by wells tested.
| County | Wells tested | Above state level | Highest | |
|---|---|---|---|---|
| Coos County, New Hampshire | 346 | 15% | 10.1 mg/L | |
| Carroll County, New Hampshire | 1,488 | 14% | 18.2 mg/L | |
| Hillsborough County, New Hampshire | 1,576 | 14% | 315 mg/L | |
| Merrimack County, New Hampshire | 3,853 | 13% | 14.2 mg/L | |
| Grafton County, New Hampshire | 1,939 | 13% | 58.1 mg/L | |
| Cheshire County, New Hampshire | 372 | 13% | 12.3 mg/L | |
| Strafford County, New Hampshire | 261 | 11% | 12.8 mg/L | |
| Sullivan County, New Hampshire | 541 | 11% | 10.4 mg/L | |
| Rockingham County, New Hampshire | 1,723 | 11% | 32.1 mg/L | |
| Belknap County, New Hampshire | 1,379 | 10% | 15.8 mg/L |
By individual samples
Counties with at least 30 individual samples in public monitoring data, against the EPA limit.
| County | Samples | Detected | Above EPA limit | Median |
|---|---|---|---|---|
| Hillsborough County, New Hampshire | 85 | 71% | 4% | 0.005 mg/L |
| Carroll County, New Hampshire | 69 | 42% | 3% | 0 mg/L |
| Merrimack County, New Hampshire | 135 | 81% | 1% | 0.005 mg/L |
| Oxford County, Maine | 33 | 100% | 0% | 0 mg/L |
| Strafford County, New Hampshire | 54 | 78% | 0% | 0 mg/L |
| Rockingham County, New Hampshire | 155 | 58% | 0% | 0 mg/L |
| Sullivan County, New Hampshire | 31 | 55% | 0% | 0.006 mg/L |
| Washington County, Maine | 45 | 47% | 0% | 0 mg/L |
| Grafton County, New Hampshire | 70 | 39% | 0% | 0 mg/L |
| Coos County, New Hampshire | 36 | 19% | 0% | 0 mg/L |
How to test
Use a state-certified lab and a proper sampling bottle; hardware-store strips cannot measure copper at the levels that matter. Collect from the kitchen tap before any treatment, and again after treatment if you install it.
How to treat
- Neutralizing filter to raise pH
- Point-of-use reverse osmosis