Nearly half of all New Hampshire residents drink water that nobody is testing for them. No utility. No regulator. Just whatever comes up through the bedrock into the pipe in your basement. If that sounds fine to you, it might be time to look more closely at what that bedrock actually contains.
New Hampshire’s geology is beautiful and genuinely complicated. The same granite formations that make the White Mountains iconic also leach arsenic, uranium, and radon directly into private wells. Pile on decades of industrial PFAS contamination and the picture gets harder to ignore. This guide explains what you’re likely dealing with, how to think through it, and when a filtration solution makes sense for your household.
The Scale of the Problem in New Hampshire
Start with this: nearly half of New Hampshire residents get their water from a private well. That’s an enormous share compared to most states, and it carries a real consequence. The quality and safety of drinking water from private domestic wells are not regulated by the Federal Government under the Safe Drinking Water Act, nor by most state governments and laws. So when something shows up in your water, there’s no utility letter, no mandatory fix, and no countdown clock. You find out when you test, or you don’t find out at all.
New Hampshire’s specific geology makes the contamination risk higher than most people expect. Naturally occurring contaminants are common in groundwater in New Hampshire. About half of the state’s bedrock wells have radon at levels of concern, and an estimated 30% have arsenic at levels that exceed the 5 ppb limit that is enforceable in public water systems. Neither of those contaminants has a taste, a smell, or a color. Your water can look perfect and still carry both.
According to the U.S. Environmental Protection Agency, a U.S. Geological Survey study of 2,100 private wells found that water pumped from about one in five wells contained one or more contaminants at concentrations exceeding a human-health benchmark for drinking water. That USGS study covered 2,100 private wells and found roughly one in five exceeded a health benchmark. In a state where the bedrock geology is as mineralized as New Hampshire’s, that national average almost certainly understates the local picture.
The Granite State Contaminant Ladder
One useful way to think about NH well water is what I call the Granite State Contaminant Ladder: a ranked view of what you’re most likely to encounter, ordered by frequency and how often it goes undetected.
| Contaminant | Source | Detectable by Taste/Smell? | NH Prevalence |
|---|---|---|---|
| Radon | Granite bedrock, naturally occurring | No | ~50% of bedrock wells |
| Arsenic | Granite bedrock, naturally occurring | No | ~30% exceed 5 ppb NH standard |
| PFAS | Industrial sites, fire suppression foam | No | Highest risk in southern NH |
| Iron & Manganese | Naturally occurring minerals | Yes (staining, metallic taste) | Very common statewide |
| Bacteria / Coliform | Septic systems, surface intrusion | Sometimes | Common in dug/shallow wells |
| Nitrate | Septic systems, fertilizer runoff | No | Localized but rising |
Prevalence figures drawn from NH Department of Environmental Services groundwater data and USGS research.
Notice that the top three contaminants on that list are all invisible. You can’t troubleshoot them by paying attention to how the water tastes, and you can’t reason your way to a result without actual test data. That’s what makes NH well water a genuine public health issue rather than just a comfort issue.
PFAS: The Contamination Layer You May Not Have Planned For
On top of the geological baseline, many NH homeowners face a second layer of contamination from industrial PFAS releases. Poly- and perfluoroalkyl substances (PFAS) are found in products used across domestic, commercial, institutional, and industrial settings, and have affected wells throughout New Hampshire but are more frequently detected at elevated levels in southern New Hampshire.
The USGS New England Water Science Center has documented this directly at the state level. In New Hampshire, estimates indicate that between 37 and nearly 50% of the population used private wells, with most living in the southern counties of Hillsborough, Merrimack, and Rockingham, which contain the state’s most populated cities and are where arsenic-contaminated groundwater is most prevalent. That geographic overlap, high population density plus the worst contamination concentrations, is what makes professional water testing so valuable rather than optional.
“Naturally occurring contaminants are common in groundwater in New Hampshire… About half of the state’s bedrock wells have radon at levels of concern.”
NH Department of Environmental Services, Drinking Water Division
A Practical Framework for Deciding What to Do Next
Here’s the honest sequence most NH homeowners should follow. Skip a step and you risk either over-investing in treatment you don’t need or under-investing and missing something serious.
- Get a baseline test first. Not a single-contaminant strip from the hardware store. A certified-lab panel that covers arsenic, radon, PFAS, bacteria, nitrate, iron, manganese, and pH. The NH Department of Environmental Services maintains a list of accredited labs and explains exactly what private well owners should test for. Your town’s geology often dictates which contaminants to prioritize.
- Map your results to treatment type. Arsenic typically calls for a reverse osmosis or oxidation-filtration system. Iron and hydrogen sulfide respond well to oxidizing filters. PFAS removal generally requires activated carbon or reverse osmosis. Bacteria needs UV treatment or chlorination. One result rarely requires one fix, which is why matching treatment to your specific test data matters.
- Consider whole-house versus point-of-use. Contaminants like iron and hydrogen sulfide affect every water outlet and warrant whole-house treatment. Arsenic and PFAS, consumed primarily through drinking, can often be addressed at the tap or under the sink. Your decision should follow your water chemistry, not a one-size approach.
- Retest after treatment is installed. A system installed for arsenic needs verification that it’s actually reducing arsenic to a safe level. Annual retests confirm the filtration media is working and help you catch any seasonal shifts in your groundwater chemistry.
Homeowners who go directly to treatment without testing first often end up with the wrong system for their actual problem. A good rule of thumb: the test result is the prescription; the filtration system is the medicine. You wouldn’t take a prescription written for someone else’s lab results.
Where to Find the Right Help
NH has more going on underground than most states, and the treatment decisions that follow from that reflect real complexity. The right system for a home in Concord with high arsenic and elevated radon looks different from a system for a dug well in Carroll County with bacteria and low pH. Certified water specialists who know the regional geology and can cross-reference your test results against local aquifer data will save you from buying equipment you don’t need, or worse, missing something you do.
If you’re in the Granite State and want to understand your options before committing to any treatment, the range of water filtration systems in New Hampshire offered by local specialists covers everything from whole-house iron reduction to PFAS-specific reverse osmosis, with certified professionals who can configure a system around your actual water chemistry rather than a generic template.
The well on your property has been there since before you moved in. The contaminants in it have been accumulating for longer than that. Testing isn’t alarmist, it’s just being a responsible homeowner in a state where the geology has opinions about what goes in your glass.
What would you do if your next water test came back with arsenic above the state limit? That’s not a hypothetical for roughly 30% of NH bedrock well owners. It’s Tuesday.
