State Well Water Guide
Delaware Private Well Water Guide
About 24% of Delawareans rely on private wells, primarily in Sussex County's rural and coastal communities and parts of Kent County. Delaware's shallow coastal plain aquifers are highly vulnerable to agricultural contamination: nitrates from poultry farming and crop production are the state's most pervasive groundwater concern. PFAS from Dover Air Force Base and industrial sites, iron and manganese from coastal plain sediments, and saltwater intrusion in coastal areas are additional risks. DNREC provides well permitting and limited oversight.
Testing Guidance
Delaware recommends annual testing for coliform bacteria and nitrates for all private wells. Sussex County well owners near poultry operations should test for nitrates and bacteria after every spring application season. Wells near Dover AFB and Route 1 industrial corridor should be tested for PFAS. Coastal well owners in Sussex County should monitor for saltwater intrusion (chloride, sodium).
What to Test For in Delaware
Total coliform bacteria and E. coli — annual minimum
Nitrates — annual for all Sussex and Kent County wells; highest priority in agricultural areas
PFAS — within 3 miles of Dover Air Force Base and industrial sites along Route 1
Iron and manganese — coastal plain aquifer wells throughout Sussex and Kent counties
Chloride and sodium — coastal Sussex County wells at risk of saltwater intrusion
Arsenic — some elevated levels found in Chesapeake and Delaware Canal area wells
pH and hardness — baseline chemistry for coastal plain well water
Common Contamination Risks in Delaware
Nitrate contamination from poultry farming and row crops — Sussex County has among the highest agricultural nitrate loading in the Mid-Atlantic
PFAS from Dover Air Force Base — one of the most significant PFAS plumes in the Mid-Atlantic region
Iron and manganese from coastal plain sediments — naturally elevated in the Piney Point and Columbia aquifers
Saltwater intrusion — sea level rise and groundwater withdrawal threaten coastal aquifer quality in lower Sussex County
Bacterial contamination from agricultural runoff — high livestock density creates pathogen risk after heavy rainfall
Contaminant Guides Relevant to DE 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 Delaware
Use the Delaware state-certified laboratory program to find accredited labs for private well testing. Always verify current certification before submitting samples.
DE Certified Lab Directory ↗Delaware 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
DE Certified Labs ↗EPA guidance
EPA Private Wells Program ↗State lab directory
DE Certified Labs ↗Minimum Annual Tests
Plus state-specific contaminants listed above
Other State Guides