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Arsenic Treatment in New Hampshire
Arsenic is naturally present in New Hampshire bedrock and is odorless and tasteless. A licensed local contractor can test your well and recommend the right system. Start with a free in-home water test and quote.
What it is and why New Hampshire wells need it
Arsenic is the contaminant that brings most New Hampshire well owners to a water test, and for good reason. It dissolves naturally out of the granite and metamorphic bedrock that underlies much of the state, and it is completely invisible, with no color, taste, or smell. The only way to know your level is to test.
A United States Geological Survey study of private bedrock wells in southeastern New Hampshire found that nearly one in five exceeded the federal arsenic limit of 10 micrograms per liter, with higher rates in parts of Hillsborough and Strafford counties. In 2021, New Hampshire set its own enforceable standard at 5 parts per billion, half the federal limit and one of the strictest in the country.
Arsenic exposure is a long-term health issue, not an emergency. NHDES and the EPA link long-term exposure to a higher risk of several cancers and other effects, which is why the state tightened its standard. The reassuring part is that arsenic is very treatable once a test shows how much is present and which form it takes.
How a contractor treats arsenic
Adsorptive media filters
Iron-based or titanium-based media bind arsenic as water passes through. A contractor can size these for the whole house or for a single tap. The media has a finite capacity and is replaced every one to three years, and its performance drops when Arsenic-III is present or pH is above 7.5.
Anion exchange
An anion exchange system trades arsenic for harmless ions on a resin bed. It removes Arsenic-V well across a range of pH and regenerates with ordinary salt, so operating costs are low. It is often paired with a calcite neutralizer for pH.
Reverse osmosis at the tap
A point-of-use reverse osmosis system under the kitchen sink pushes water through a fine membrane and removes about 95 percent of Arsenic-V. Because it treats only one tap, it is a lower-cost option for drinking and cooking water.
Why the arsenic species matters
Arsenic shows up as Arsenic-III or Arsenic-V. Arsenic-III carries no electrical charge, so anion exchange and membranes remove it less effectively. A contractor may add a simple pre-oxidation step, using chlorine or a manganese dioxide media, to convert Arsenic-III to the more easily removed Arsenic-V before the main treatment.
What to expect
- 1
Request a free in-home water test
Use the form or call. A licensed local contractor sets up a visit at no cost.
- 2
The contractor tests your water and reviews the results
You get a plain explanation of what is in your water and what it means.
- 3
You get a written, itemized recommendation and quote
If treatment makes sense, the recommendation is matched to your water, with the cost in writing.
- 4
The contractor installs the system
If you choose to proceed, the contractor installs and configures the system for your home.
- 5
The contractor confirms performance and explains maintenance
You leave with a clear maintenance schedule and, where relevant, a retest plan.
For arsenic, NHDES recommends retesting the treated water quarterly for the first year and twice a year after that, so you can confirm the system is doing its job.
What arsenic treatment costs in New Hampshire
NHDES guidance puts a typical whole-house arsenic system, whether adsorptive media or anion exchange followed by a calcite neutralizer, at roughly $1,500 to $3,000 to install, with the main ongoing cost being a replacement filter every one to three years. A point-of-use reverse osmosis system that treats only the kitchen tap costs less.
Your real number depends on your arsenic level, the arsenic species, your pH, and whether other contaminants are present, which is exactly what the free in-home test and written quote sort out. These figures are 2026 New Hampshire market context drawn from NHDES guidance, not a quote.
Where this fits
Related services a contractor often pairs with this one:
Serving well owners in these and other New Hampshire towns:
Read: New Hampshire Arsenic in Well Water: A Homeowner's GuideFrequently Asked Questions
How does arsenic get into New Hampshire well water?
It occurs naturally. Arsenic dissolves out of the granite and metamorphic bedrock that underlies much of New Hampshire, so it shows up in bedrock wells without any nearby pollution source.
What is New Hampshire's arsenic standard?
New Hampshire lowered its enforceable arsenic standard to 5 parts per billion in 2021, half the federal limit of 10 parts per billion. Testing is the only way to know where your well falls.
Should I treat the whole house or just the kitchen tap?
It depends on your level and whether other contaminants are present. Because arsenic is not absorbed through the skin, a point-of-use system at the kitchen tap is often enough, while higher levels or other contaminants may call for a whole-house system. The contractor recommends the right approach after testing.
Does an arsenic system need maintenance?
Yes. Adsorptive media is replaced every one to three years, and reverse osmosis membranes and cartridges are changed on a schedule. The contractor explains the maintenance plan in the written quote.
What is the difference between Arsenic-III and Arsenic-V?
They are two forms of arsenic. Arsenic-III has no electrical charge and is harder to remove, so a contractor may add a pre-oxidation step to convert it to Arsenic-V, which anion exchange and reverse osmosis remove more effectively.
How soon should I retest after treatment?
NHDES recommends retesting treated water for arsenic quarterly during the first year and twice a year after that.
Start with a free in-home water test
A licensed local contractor will test your water, explain the results, and give you a written quote. No obligation.