Well Water in Londonderry, New Hampshire

Rockingham County · Population ~26,000 · Aquifer: Glacial Till / Bedrock

Hardness: Moderate to Hard

Arsenic: A Primary Concern

Londonderry falls within the southeastern NH arsenic belt — an area where granitic and metamorphic bedrock naturally releases arsenic into groundwater. The NH Geological Survey maps Londonderry as having moderate to high arsenic probability.

Statewide, approximately 30% of tested wells exceed the EPA arsenic standard of 10 µg/L. In some southeastern towns, the rate is even higher. Arsenic is invisible — no taste, no smell, no color. You must test.

NH was one of the first states to systematically study arsenic in private wells. The data is clear: if you're on a bedrock well in Londonderry, arsenic testing is essential. See our arsenic guide.

Radon in Groundwater

The same granite that produces arsenic also produces radon — a radioactive gas that dissolves into groundwater. When radon-containing water is used indoors, the gas is released into the air you breathe.

NH has some of the highest radon levels in the country, both in indoor air and in well water. Londonderry's granitic geology makes radon testing a priority. See our radon guide.

PFAS Awareness

While Londonderry is not within the Saint-Gobain plume, PFAS contamination in NH is not limited to a single source. Multiple sites across the state have been identified, and PFAS can travel significant distances through groundwater.

NH DES recommends PFAS testing for all private wells, particularly those near airports, fire training facilities, landfills, or industrial sites. See our PFAS guide.

Testing and Treatment

Londonderry well owners should test for arsenic, radon, bacteria, nitrates, manganese, uranium, hardness, pH, and conductivity. Consider PFAS testing as well.

Treatment systems are available for all common NH contaminants, and NH rebates of $5,000-$10,000 can offset the cost significantly. See our testing guide for certified labs.