State Well Water Guide
Connecticut Private Well Water Guide
Approximately 22% of Connecticut residents rely on private wells, with the highest concentrations in eastern and northwestern Connecticut. Connecticut's granite and metamorphic bedrock releases naturally occurring arsenic, radon, and uranium — with radon-in-water levels among the highest in the nation for affected wells. Industrial legacy contamination is significant: Connecticut's Naugatuck River Valley and other industrial corridors have well-documented VOC plumes from former metal manufacturing and plating operations. Connecticut DPH certifies labs and provides well testing guidance through the Private Well Testing Act, which requires testing at point of sale.
Testing Guidance
Connecticut DPH recommends annual testing for bacteria. Test for arsenic, radon, and uranium at purchase and every 5 years thereafter. The Connecticut Private Well Testing Act (2022) requires testing at property transfer — review results carefully. Wells near the Naugatuck Valley, Shelton, Derby, or Ansonia industrial corridor should be tested for VOCs. PFAS testing is warranted near military installations and airports (Bradley International, Groton Naval Submarine Base).
What to Test For in Connecticut
Total coliform bacteria and E. coli — annual minimum
Arsenic — statewide from crystalline bedrock; CT has relatively high prevalence
Radon in water — among highest in the U.S. from granite; especially northwestern CT
Uranium — bedrock wells statewide; often co-elevated with arsenic and radon
Volatile organic compounds — Naugatuck Valley industrial corridor, former dry cleaners, gas stations
PFAS — near Groton Submarine Base, Bradley International Airport, Sikorsky Aircraft facilities
Nitrates — eastern CT agricultural areas, areas with septic systems
Lead — homes built before 1986
Common Contamination Risks in Connecticut
Radon dissolved in water from granite — Connecticut has some of the highest radon-in-water concentrations documented in the Northeast; Tolland, Windham, and Litchfield counties are most affected
Naturally occurring arsenic from crystalline bedrock — documented in all CT counties; crystalline Highland Wells tend to have higher concentrations
VOC contamination from industrial legacy — Naugatuck Valley manufacturing heritage left extensive chlorinated solvent plumes in shallow aquifers affecting private wells in Shelton, Derby, Ansonia, and Naugatuck
PFAS from military and aviation — Groton Naval Submarine Base and Bradley International Airport have documented PFAS plumes from AFFF firefighting foam
Uranium from bedrock — Connecticut bedrock wells have documented uranium above the EPA MCL of 30 µg/L in some areas
Coliform from aging well construction — older drilled and dug wells in rural CT are vulnerable to contamination; retesting after flooding is essential
Contaminant Guides Relevant to CT 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 Connecticut
Use the Connecticut state-certified laboratory program to find accredited labs for private well testing. Always verify current certification before submitting samples.
CT Certified Lab Directory ↗Connecticut 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
CT Certified Labs ↗EPA guidance
EPA Private Wells Program ↗State lab directory
CT Certified Labs ↗Minimum Annual Tests
Plus state-specific contaminants listed above
Other State Guides