Well Water in Derry, New Hampshire

Rockingham County · Population ~34,000 · Aquifer: Glacial Till / Bedrock

Hardness: Moderate to Hard

Derry is one of the most populated towns in NH, and many residents in outlying areas depend on private wells drawing from glacial till and fractured bedrock. The granitic geology produces the same arsenic and radon concerns found throughout southeastern New Hampshire.

Arsenic in Bedrock Wells

Derry's bedrock is predominantly granitic and metamorphic — rock types that are well-documented sources of naturally occurring arsenic in New Hampshire. The NH Geological Survey has identified Derry as an area with elevated arsenic probability.

Arsenic dissolves from bedrock into groundwater over time. Deeper wells and wells in certain bedrock formations tend to have higher arsenic. But there's enormous variability — two wells on the same street can have very different arsenic levels depending on the exact bedrock they penetrate.

See our arsenic guide for health effects at different concentrations and treatment options.

Radon and Uranium

Granite contains trace amounts of uranium, which decays to produce radon gas. Derry wells commonly have elevated radon in water — the gas dissolves into groundwater and is released indoors when water is used.

Uranium itself can also be present at concerning levels in some wells. The EPA maximum contaminant level for uranium is 30 µg/L. Both radon and uranium should be tested at least once.

See our radon guide for more on radon in NH well water.

What to Test For

Derry well owners should test for: arsenic, radon, uranium, bacteria (total coliform and E. coli), nitrates, manganese, iron, hardness, pH, and conductivity.

If treatment is needed, check whether you qualify for NH's well water treatment rebates — up to $5,000-$10,000 toward a treatment system.

See our testing guide for labs and costs.

NH Treatment Rebates: If your well water exceeds any health-based standards, you may be eligible for $5,000-$10,000 in state rebates toward a treatment system. Check your eligibility.

Every well is different. Two wells on the same street can produce completely different water. The data on this page reflects documented conditions in the Derry area, but the only way to know what's in your water is to test it.

Sources

  • NH Geological Survey — Arsenic Probability Maps
  • USGS — Uranium and Radon in New England Groundwater
  • NH DES — Private Well Testing Data for Rockingham County