The state makes your seller hand you a radon notification. That piece of paper is not a test — and it says nothing about what comes out of the tap.
One in Three New Hampshire Homes — and Almost Nobody Tests the Water
Nationally, roughly one home in fifteen sits at or above the EPA’s radon action level of 4.0 pCi/L. In New Hampshire, according to the state Department of Health and Human Services, it is closer to one in three.
“The Granite State” is not just a license-plate slogan. The bedrock under most of New Hampshire is uranium-bearing granite, and as that uranium decays it releases radon — along with arsenic — into the soil gas and the groundwater. Outside the downtown cores of Manchester, Nashua, Concord and Portsmouth, most homes draw from private wells drilled straight into that bedrock.
That gives radon two ways into a house, not one. It seeps up through foundation cracks, sump pits and slab seams. And it rides in dissolved in the well water, then releases into the air every time someone runs a shower, a dishwasher or a washing machine. Buyers routinely test the first path. Very few test the second.
The Notification Is Not a Test Result
Under RSA 477:4-a, a New Hampshire seller must give the buyer a written notification before the purchase and sale contract is executed. It states that radon “may be found in some areas of New Hampshire,” that it “may pass into a structure through the ground or through water from a deep well,” and that testing by a certified professional and an accredited lab can establish whether it is present. The buyer signs to acknowledge receipt.
The statute requires notification, not testing. It does not require the seller to produce a number, and it does not require anyone to fix anything. Signing means you were told radon exists in New Hampshire — nothing more. Plenty of buyers file the form with the closing packet and treat the signature line as a clearance.
RSA 477:4-d goes a step further for private water supplies: the seller must disclose the type and location of the well, the date of the most recent water test, and any known problems. On a large share of New Hampshire listings, that “date of most recent test” line comes back blank, or lists a test from a decade and two owners ago.
Water Radon Becomes Air Radon
The rule of thumb used across New England: for roughly every 10,000 pCi/L of radon in water, about 1 pCi/L ends up in the air of the house. That sounds negligible until you see what bedrock wells in Rockingham, Hillsborough and Strafford counties actually return — results in the thousands to tens of thousands of pCi/L are not unusual here.
New Hampshire’s guidance is to consider treating the water when it falls between 2,000 and 10,000 pCi/L and the airborne level is 4.0 pCi/L or higher. The EPA, which does not regulate private wells at all, suggests treatment at or above 4,000 pCi/L.
The practical consequence matters at the closing table: a home that mitigates the soil pathway alone while continuing to pump high-radon water may never settle below the action level. And the fix is not trivial. A water aeration system commonly runs $4,000 to $6,000, and homes needing both air mitigation and water treatment often land in the $6,000 to $15,000 range. Those are numbers to negotiate during due diligence, not discover in year two.
What the Testing Actually Involves
When FPI inspects a New Hampshire home on a private well, radon testing is not a separate errand:
- A 48-hour short-term air test placed in the lowest livable level, under closed-house conditions
- A water sample drawn from an interior tap without aeration and delivered to an accredited laboratory
- Companion well-water screening on the same sample trip — arsenic, uranium, nitrate, bacteria and PFAS all trace back to the same bedrock and the same land use
- Inspection of the wellhead and cap seal, pressure tank and observed flow
- Results delivered with the inspection report, timed to land inside the contingency window
For Agents: Managing the Radon Conversation
The RSA 477:4-a notification is a disclosure, not a warranty. It does not shield anyone from a buyer blindsided by a $9,000 remediation quote six months after closing. Document in writing that you advised testing — and that the buyer accepted or declined.
On the listing side, testing before you go to market is almost always the better play. New Hampshire inventory is up from the 2021–2023 lows but still thin on the Seacoast, and sellers there have room to control the narrative. A tested home with a mitigation system already installed reads as handled, not defective.
For buyers, order the air and water tests together at the inspection rather than sequentially. Lab turnaround on the water sample is the item most likely to blow a tight contingency date — build it into the deadline before you sign.
Test Both Pathways Before You Close
Focused Property Inspections tests radon in both air and water, along with full well-water panels covering arsenic, uranium, nitrate, bacteria and PFAS — plus septic evaluations, buried oil tank sweeps, chimney inspections and complete home inspections across New Hampshire and Maine. Reports are delivered the same day, so your findings arrive while you still have leverage.
Schedule your inspection today.
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