State Well Water Guide
New Hampshire Private Well Water Guide
New Hampshire has the highest proportion of residents relying on private wells of any New England state — approximately 55%, or over 700,000 people. The state's granite bedrock is a source of naturally occurring arsenic (approximately 10–15% of wells exceed 10 ppb), radon, and uranium. New Hampshire is also home to one of the most extensively studied PFAS contamination sites in the U.S.: Pease International Tradeport in Portsmouth, a former U.S. Air Force base where PFAS from AFFF firefighting foam contaminated the municipal supply and nearby private wells. NH DES provides one of the more proactive state private well programs in the region.
Testing Guidance
NH DES recommends testing all private wells annually for bacteria and nitrates. For bedrock wells, test for arsenic, uranium, and radon in water every 3–5 years. New homeowners should conduct a full baseline panel before occupying. Wells within 3 miles of Pease Tradeport or any former military or industrial site with known PFAS should be tested. If your home has older plumbing, include lead and copper in your test.
What to Test For in New Hampshire
Total coliform bacteria and E. coli — annual minimum
Arsenic — all bedrock wells; 10–15% exceed EPA MCL in NH
Radon in water — granite state; among highest radon in groundwater in U.S.
Uranium — co-occurs with arsenic in granitic bedrock wells
PFAS — wells near Pease International Tradeport, Manchester Airport, former industrial sites
Nitrates — wells near agriculture, large lawns with fertilizer, or septic systems
Manganese — naturally elevated in many NH bedrock wells; neurotoxic at high levels
Lead — homes with older plumbing or galvanized service lines
Common Contamination Risks in New Hampshire
Naturally occurring arsenic from granite — approximately 10–15% of NH private wells exceed 10 ppb; highest in Merrimack, Hillsborough, and Rockingham counties
PFAS contamination from Pease International Tradeport — documented PFAS plume from former Air Force firefighting operations; NH DES has tested thousands of wells in the area
Radon dissolved in groundwater — New Hampshire granite is one of the most radon-productive rock types in the Northeast
Uranium from granitic geology — detected in wells across the state; elevated uranium correlates with arsenic-prone formations
Manganese from bedrock fractures — health concerns at elevated levels, particularly for infants and young children
Coliform bacteria from poorly constructed or aging dug wells — particularly in older rural properties
Contaminant Guides Relevant to NH Wells
PFAS
Synthetic Chemicals
EPA limit: 4 ppt
Lead
Heavy Metals
EPA limit: 15 ppb (action level)
Nitrates
Agricultural Chemicals
EPA limit: 10 mg/L
DBPs
Disinfection Byproducts
EPA limit: 80 µg/L (TTHMs) / 60 µg/L (HAA5)
Arsenic
Heavy Metals
EPA limit: 10 ppb
Hard Water
Minerals
EPA limit: No federal limit
Chlorine
Disinfection Chemicals
EPA limit: 4 mg/L (MRDL)
Microplastics
Emerging Contaminants
EPA limit: No federal limit
Bacteria
Microbial Contamination
EPA limit: Zero E. coli / < 1 coliform per 100 mL
Fluoride
Minerals
EPA limit: 4 mg/L (MCL) / 2 mg/L (Secondary MCL)
Chromium-6
Heavy Metals
EPA limit: 100 ppb (total chromium)
Copper
Heavy Metals
EPA limit: 1.3 mg/L (action level)
Radon
Radioactive Contaminants
EPA limit: No finalized MCL
Iron & Manganese
Minerals
EPA limit: 0.3 mg/L iron / 0.05 mg/L manganese (aesthetic SMCLs)
Atrazine
Agricultural Chemicals
EPA limit: 3 ppb (0.003 mg/L)
Uranium
Radioactive Contaminants
EPA limit: 30 µg/L (30 ppb)
Perchlorate
Industrial Chemicals
EPA limit: 0.056 mg/L (56 ppb)
VOCs
Industrial Chemicals
EPA limit: Varies by compound: benzene 5 ppb; TCE 5 ppb; PCE 5 ppb; vinyl chloride 2 ppb
Radium
Radioactive Contaminants
EPA limit: 5 pCi/L (combined Ra-226 + Ra-228)
Crypto & Giardia
Microbial Contamination
EPA limit: Zero (treatment technique standard)
Hydrogen Sulfide
Naturally Occurring Compounds
EPA limit: No MCL; Secondary MCL (aesthetic) of 0.05 mg/L
Selenium
Minerals
EPA limit: 50 ppb (0.05 mg/L)
Cadmium
Heavy Metals
EPA limit: 5 ppb (0.005 mg/L)
Mercury
Heavy Metals
EPA limit: 2 ppb (0.002 mg/L)
Barium
Heavy Metals
EPA limit: 2 mg/L
Find a Certified Lab in New Hampshire
Use the New Hampshire state-certified laboratory program to find accredited labs for private well testing. Always verify current certification before submitting samples.
NH Certified Lab Directory ↗New Hampshire Well Water FAQs
Related Pages
Data Sources & Provenance
All data on this page is sourced from official U.S. government or public datasets.
Quick Reference
State program
NH Certified Labs ↗EPA guidance
EPA Private Wells Program ↗State lab directory
NH Certified Labs ↗Minimum Annual Tests
Plus state-specific contaminants listed above
Other State Guides