State Well Water Guide
Maryland Private Well Water Guide
About 25% of Marylanders — approximately 1.5 million people — rely on private wells, primarily in the rural Eastern Shore, Western Maryland, and suburban fringes of the Washington DC and Baltimore metro areas. Maryland's diverse geology creates distinct regional risks: arsenic and radon in the crystalline rock of Frederick and Carroll counties, nitrates and agricultural contaminants on the Eastern Shore, PFAS from military installations, and iron/manganese throughout the coastal plain. Maryland's Environmental Regulations require certain well construction standards but do not mandate ongoing testing.
Testing Guidance
Maryland MDE recommends annual testing for coliform bacteria, nitrates, and pH. Western Maryland and Piedmont well owners should test for arsenic and radon. Eastern Shore well owners should prioritize nitrates and agricultural chemicals. Wells near military facilities (Aberdeen Proving Ground, Naval Air Station Patuxent River, Fort Meade) should be tested for PFAS.
What to Test For in Maryland
Total coliform bacteria and E. coli — annual minimum
Nitrates — especially Eastern Shore agricultural areas and areas with dense septic
Arsenic — Piedmont and Blue Ridge crystalline rock wells (Frederick, Carroll, Baltimore, Harford counties)
Radon — crystalline rock areas of Western Maryland and the Piedmont
PFAS — within 3 miles of Aberdeen Proving Ground, NAS Patuxent River, Fort Meade, and Andrews AFB
Iron and manganese — coastal plain aquifer wells on the Eastern Shore and southern Maryland
TCE — near Aberdeen Proving Ground and industrial areas of the Baltimore metro
pH and hardness — particularly in acidic, low-pH groundwater areas of the Piedmont
Common Contamination Risks in Maryland
Arsenic from crystalline bedrock — the Piedmont Province has naturally elevated arsenic concentrations in groundwater
Radon from uranium-bearing granites — Western Maryland and the Piedmont have elevated radon in both well water and indoor air
Nitrates from agriculture — the Eastern Shore's intensive agriculture and poultry industry creates severe nitrate loading in shallow aquifers
PFAS from military installations — multiple major military facilities with AFFF histories are significant contamination sources
Iron and manganese from coastal plain sediments — naturally elevated levels throughout the Eastern Shore and southern Maryland aquifers
Contaminant Guides Relevant to MD 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 Maryland
Use the Maryland state-certified laboratory program to find accredited labs for private well testing. Always verify current certification before submitting samples.
MD Certified Lab Directory ↗Maryland 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
MD Certified Labs ↗EPA guidance
EPA Private Wells Program ↗State lab directory
MD Certified Labs ↗Minimum Annual Tests
Plus state-specific contaminants listed above
Other State Guides