Arsenic in Drinking Water in New Hampshire
What residents of New Hampshire need to know about arsenic in drinking water — including natural geological sources, private well risk, which utilities have documented violations, and how to remove arsenic from tap water.
Source: EPA SDWIS, New Hampshire Department of Environmental Services, USGS · Last reviewed: 2025-01-01
Quick Answer
Is arsenic in drinking water a concern in New Hampshire?
Yes — New Hampshire is one of the most arsenic-affected states in the country for private well users. The state's granite and metamorphic bedrock is naturally arsenic-bearing, and approximately 40% of New Hampshire residents use private wells drilled into this bedrock. Studies have found that a substantial fraction of New Hampshire bedrock wells exceed the 10 ppb MCL, and the state has one of the most active private well testing programs in the Northeast.
Where does arsenic come from in New Hampshire's water?
Granite, schist, and other metamorphic bedrock formations are the overwhelmingly dominant arsenic source in New Hampshire. Private wells drilled into these formations — standard for rural New Hampshire — leach arsenic from naturally occurring arsenic-bearing minerals. Arsenic occurs in pyrite and arsenopyrite minerals distributed throughout the granite and metamorphic rock. No contamination event or human activity is required — the arsenic is intrinsic to the geology.
What should New Hampshire residents know?
All New Hampshire private well owners should test for arsenic — it is the most important water quality test for NH well owners. New Hampshire DES recommends testing before purchase of any property with a well, at every real estate transfer, and every 3–5 years for existing users. Standard pitcher filters do not remove arsenic. Reverse osmosis or NSF-certified activated alumina is required. New Hampshire DES provides guidance and a certified laboratory list.
Key Facts
| EPA MCL | 10 µg/L (10 ppb) |
| MCLG | Zero |
| Primary source | Granite and metamorphic bedrock — naturally arsenic-bearing New England crystalline geology |
| Private well rate | ~40% of NH residents on private wells — 10–20%+ of bedrock wells may exceed MCL |
| State requirement | Arsenic testing required at real estate transfer; reimbursement program for low-income owners |
| State regulator | New Hampshire Department of Environmental Services (DES) |
| Health effects | Bladder, lung, skin cancer; cardiovascular; diabetes risk |
| Effective treatment | Reverse osmosis or activated alumina — pitcher filters do NOT remove arsenic |
Why Arsenic Matters in New Hampshire
New Hampshire has among the highest rates of private well arsenic occurrence of any state east of the Mississippi. Studies have consistently found that 10–20% or more of New Hampshire bedrock wells exceed the 10 ppb MCL, with some areas having much higher rates. Rockingham, Hillsborough, Merrimack, and Strafford counties have some of the highest documented rates, but arsenic occurs throughout the state. New Hampshire DES has been proactive — requiring arsenic testing at real estate transfer, providing public education, and operating a private well testing reimbursement program for low-income residents.
New Hampshire Arsenic Program
New Hampshire DES has documented extensive arsenic in private wells across the state's crystalline granite bedrock. New Hampshire has one of the highest rates of private well arsenic exceedance in New England. The state offers private well testing guidance and maintains a well testing database. DES recommends arsenic testing for all private wells, with particular emphasis in Hillsborough, Merrimack, and Belknap counties.
New Hampshire Utilities With Arsenic Violation Records
The utilities listed below have at least one arsenic violation on record in EPA's SDWIS database. Violations may be open or resolved — see individual utility pages for current status and risk level.
How Does Arsenic Get Into Drinking Water?
Arsenic in drinking water is almost always naturally occurring — it leaches from arsenic-bearing rocks and minerals into groundwater over time. New England granite, Southwest volcanic geology, and Upper Midwest glacial aquifers are the primary high-risk formations. It has no taste, odor, or color.
Full arsenic overview — geology maps, health effects, all 50 statesWho Should Pay Closest Attention
Private well owners throughout New Hampshire face significant arsenic risk from bedrock geology. Rockingham County (Seacoast area), Hillsborough County (Manchester/Nashua suburbs), Merrimack County, and Strafford County have high documented occurrence rates, but no county is free of risk.
Private well owners near mining districts or agricultural areas
Residents in states with documented volcanic or geothermal geology
Long-term consumers of water from small groundwater systems
Households in homes built before 1960 with older well casings
Residents whose well water has never been tested for arsenic
Anyone living in a state where bedrock wells are common
How to Check Your Situation in New Hampshire
- 1
Identify your water source. If you use a public utility, use the ZIP lookup on this page to find your system and check its compliance record.
- 2
If on public water, review your utility's most recent Consumer Confidence Report (CCR) for arsenic monitoring data. The MCL is 10 ppb — your report should show recent test results.
- 3
If on a private well, order an arsenic test from a New Hampshire Department of Environmental Services-certified laboratory. A basic arsenic test costs $15–$40. The state agency website maintains a certified lab list.
- 4
Test your well at the tap — not just at the wellhead. The entire water distribution system within your home can affect water quality.
- 5
If your test shows arsenic above 5 ppb, install certified treatment immediately. If above 10 ppb, do not use the water for drinking or cooking until treatment is installed.
- 6
Retest after installing treatment to confirm it is working as certified. Replace filter media on the manufacturer's schedule — an exhausted filter may not perform as rated.
Treatment Options for Arsenic
Boiling does not remove arsenic — it concentrates it. Standard activated carbon filters (Brita, etc.) do not effectively remove arsenic. Certified treatment is required.
NSF/ANSI Standard 58 — Reverse Osmosis
RO systems certified to NSF/ANSI 58 remove 85–95% of arsenic. Under-sink installation. Most effective for removing multiple contaminants simultaneously. Replace membranes and pre-filters on schedule.
Activated Alumina Filters
Activated alumina is specifically designed for arsenic and fluoride removal. Point-of-use or whole-house options available. Must be certified by NSF International or WQA for arsenic reduction. Requires periodic media regeneration or replacement.
Iron/Manganese Oxidation Filters
Effective for arsenic in iron-rich well water, which is common in the Midwest and New England. Oxidation converts dissolved iron and arsenic to a form that can be filtered out. Best when arsenic is co-occurring with high iron levels.
What does NOT work for arsenic
Standard activated carbon filters (Brita, refrigerator filters, most pitcher filters) do NOT effectively remove arsenic. Boiling concentrates arsenic. Water softeners do not remove arsenic. Only use products with NSF certification specifically for arsenic reduction.
Take Action Now
If you use a private well in New Hampshire, test for arsenic — especially if you are in a region with granite, volcanic, or sedimentary geology. A basic arsenic test costs $15–$40 at a state-certified lab.
Public water users: check your utility's Consumer Confidence Report (CCR) for arsenic results. The EPA MCL is 10 ppb — any detection warrants attention.
If arsenic is detected above 10 ppb (or even below it, given MCLG is zero), install an NSF/ANSI 58-certified reverse osmosis system for drinking and cooking water.
Standard carbon filters do NOT remove arsenic — do not rely on a Brita or refrigerator filter for arsenic protection.
Frequently Asked Questions
Related Pages
Arsenic — National Overview
All U.S. utilities with arsenic records
New Hampshire State Overview
All utilities and water quality data
New Hampshire Well Water Guide
Testing, risks & certified labs for private wells
Reverse Osmosis Guide
Removes 85–95% of arsenic
Best Arsenic Filter Guide
What actually works (carbon doesn't)
PFAS in Drinking Water
The 'forever chemical' contamination overview
All Contaminants
Complete reference library
Data Sources & Provenance
All data on this page is sourced from official U.S. government or public datasets.
Find Your Utility
State Regulator
New Hampshire Department of Environmental Services ↗