State Well Water Guide
Missouri Private Well Water Guide
About 30% of Missourians rely on private wells, with the highest rates in the rural Ozarks, agricultural northwest and northeast corners, and Bootheel region. Missouri's Ozark Plateau — one of the largest karst regions in North America — creates a highly permeable groundwater system where bacterial contamination from agricultural and septic sources can reach wells rapidly. The southeast Missouri Bootheel has Delta-style agricultural contamination. PFAS from military sites, naturally occurring radium in some deep aquifers, and industrial contamination in the St. Louis metropolitan area are additional concerns. MDNR regulates well construction.
Testing Guidance
Missouri DNR recommends annual testing for coliform bacteria and nitrates. Ozark karst well owners should test quarterly for bacteria given rapid aquifer recharge. Bootheel region well owners should prioritize nitrates. Northwest Missouri well owners near hog confinement operations should test for bacteria and nitrates. Wells near Whiteman AFB and Fort Leonard Wood should be tested for PFAS.
What to Test For in Missouri
Total coliform bacteria and E. coli — annual minimum; quarterly for Ozark karst wells
Nitrates — agricultural areas statewide; Bootheel, northwest, and northeast Missouri
PFAS — near Whiteman AFB, Fort Leonard Wood, and Lambert St. Louis Airport
Radium and uranium — some deep Ordovician/Cambrian aquifer wells in the Ozarks
Iron and manganese — glacial drift wells in northern Missouri and alluvial wells in the Bootheel
Agricultural chemicals — wells in intensive agricultural areas
Volatile organic compounds — near St. Louis metropolitan industrial areas
Common Contamination Risks in Missouri
Karst aquifer vulnerability — the Ozark Plateau's extensive cave and spring systems allow rapid unfiltered transmission of agricultural and septic contamination to wells
Nitrate from agricultural sources — northwest and northeast Missouri's grain and hog farming create significant nitrogen loading to groundwater
Bacterial contamination from swine CAFOs — Missouri is a major hog producer; manure from large operations can contaminate nearby wells
PFAS from military sites — Whiteman AFB and Fort Leonard Wood are identified PFAS sources
Agricultural contamination in the Bootheel — the Southeast Missouri Bootheel's cotton, soybean, and rice agriculture parallels Delta contamination patterns
Contaminant Guides Relevant to MO 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 Missouri
Use the Missouri state-certified laboratory program to find accredited labs for private well testing. Always verify current certification before submitting samples.
MO Certified Lab Directory ↗Missouri 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
MO Certified Labs ↗EPA guidance
EPA Private Wells Program ↗State lab directory
MO Certified Labs ↗Minimum Annual Tests
Plus state-specific contaminants listed above
Other State Guides