Chloride in New Hampshire well water
In New Hampshire, 3% of 20,353 private wells tested between 2006 and 2020 had chloride above the New Hampshire guidance level (250 mg/L), according to NH DHHS.
Chloride mainly comes from road salt and water softener discharge. Above 250 mg/L water tastes salty and corrodes plumbing. Rising chloride in a well usually means road salt is reaching the aquifer.
Check your chloride number
Type the value from your lab report. It is compared to the New Hampshire guidance level and the EPA limit, the same way the full interpretation does it.
Test your New Hampshire well for chloride
Certified lab analysis of your own tap water, bottles and prepaid return shipping included. The Essential well panel covers arsenic, uranium, nitrate, lead, copper, manganese, iron, sodium and bacteria; radon and PFAS are add-ons.
Order the Tap Score well water test kit, from $209Already tested? Upload the report
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Systems that remove chloride
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Some links below are affiliate links. If you buy through one, the merchant pays us a commission at no extra cost to you. It does not change which products we list or what the data says.
For chloride
Under-sink reverse osmosis system
under-sink or countertop, about $300
Look for NSF/ANSI 58 certification listing the contaminant you need removed.
Rather have it installed and sized for your well? Book a free in-home water test with a licensed local company.
Where to get a well tested for chloride in New Hampshire: certified labs, state programs and prices.
By county, from homeowner tests
Share of private wells above the state guidance level (250 mg/L) in tests homeowners sent to the state lab, 2006 to 2020.
| County | Above state level | Wells tested | Highest |
|---|---|---|---|
| Rockingham | 3,020 | 2,490 mg/L | |
| Belknap | 1,725 | 2,140 mg/L | |
| Strafford | 560 | 1,300 mg/L | |
| Hillsborough | 3,631 | 1,300 mg/L | |
| Cheshire | 639 | 660 mg/L | |
| Carroll | 1,832 | 1,300 mg/L | |
| Merrimack | 4,897 | 3,300 mg/L | |
| Grafton | 2,688 | 1,800 mg/L | |
| Coos | 623 | 670 mg/L | |
| Sullivan | 738 | 830 mg/L |
Towns with the highest share above the state level
- Mont Vernon, Hillsborough County17% of 47 wells
- Chesterfield, Cheshire County16% of 50 wells
- Hampton Falls, Rockingham County16% of 45 wells
- East Kingston, Rockingham County13% of 32 wells
- Laconia, Belknap County12% of 57 wells
- Auburn, Rockingham County11% of 72 wells
- Candia, Rockingham County11% of 82 wells
- Center Harbor, Belknap County11% of 95 wells
- Atkinson, Rockingham County10% of 115 wells
- New Durham, Strafford County10% of 58 wells
- Plaistow, Rockingham County10% of 259 wells
- Canaan, Grafton County10% of 95 wells
- Sandown, Rockingham County10% of 74 wells
- Sugar Hill, Grafton County9% of 54 wells
- Kingston, Rockingham County9% of 76 wells
- Newton, Rockingham County8% of 48 wells
- Hooksett, Merrimack County8% of 155 wells
- Stratham, Rockingham County7% of 109 wells
- Durham, Strafford County7% of 55 wells
- Salisbury, Merrimack County7% of 111 wells
- Belmont, Belknap County7% of 162 wells
- Moultonborough, Carroll County7% of 333 wells
- Salem, Rockingham County7% of 92 wells
- Chester, Rockingham County7% of 92 wells
- Derry, Rockingham County6% of 109 wells
By county, from individual samples
Public monitoring samples against the EPA limit; counties with at least 30 samples.
| County | Above EPA limit | Samples | Detected | Median | Highest |
|---|---|---|---|---|---|
| Rockingham | no limit | 356 | 95% | 26.7 | 559 mg/L |
| Cheshire | no limit | 101 | 92% | 10 | 220 mg/L |
| Strafford | no limit | 106 | 90% | 9.65 | 790 mg/L |
| Hillsborough | no limit | 229 | 85% | 11 | 509 mg/L |
| Sullivan | no limit | 46 | 78% | 5.5 | 290 mg/L |
| Carroll | no limit | 275 | 77% | 5 | 654 mg/L |
| Coos | no limit | 175 | 66% | 3.2 | 547 mg/L |
| Belknap | no limit | 182 | 65% | 3 | 188 mg/L |
| Merrimack | no limit | 537 | 65% | 2 | 435 mg/L |
| Grafton | no limit | 246 | 64% | 2 | 389 mg/L |
Sources
- NH DHHS WISDOM private well summaries: Town summaries of private well tests run by the New Hampshire Public Health Laboratories, published by NH DHHS through the WISDOM environmental public health tracking portal. Exceedance shares use New Hampshire guidance levels, which are stricter than EPA for arsenic (5 ug/L), manganese (0.3 mg/L), radon (2,000 pCi/L) and sodium (20 mg/L). Statistics for small counts are suppressed (*). Retrieved September 3, 2026.
- Individual samples from the USGS Water Quality Portal and state monitoring, summarized per geography. chloride counts and shares are listed on each county and town page with their sources.