State Well Water Guide
Ohio Private Well Water Guide
Ohio has over 800,000 private wells serving approximately 2 million residents, concentrated in rural areas outside municipal water service areas. Ohio's glacial geology, agricultural intensity, and legacy industrial history create a complex contamination landscape. Primary concerns include nitrate from agriculture and septic systems, bacteria from karst geology in northwest Ohio and the limestone belt, lead from older well pump and pressure tank components, and PFAS from industrial sources concentrated in the northeastern and central portions of the state.
Testing Guidance
Ohio EPA and Ohio State University Extension recommend testing private wells annually for bacteria (total coliform and E. coli) and nitrates. Additional testing is advised for: radon (Ohio ranks among the higher radon states — test indoor air first, then water if air levels are elevated), PFAS (near Scioto and Muskingum River industrial corridors, near military installations), arsenic (southern Ohio, particularly in areas with Ordovician shale), and volatile organic compounds (near legacy industrial sites in northeastern Ohio). All new wells should receive a baseline comprehensive test.
What to Test For in Ohio
Total coliform bacteria and E. coli — annual minimum for all wells
Nitrates — annual for wells near cropland or septic systems; Ohio agriculture is intensive
Lead — older pressure tanks, well pumps, and household plumbing; Ohio has significant pre-1986 housing stock
Radon — Ohio has elevated geological radon; test indoor air first, then water if air levels warrant
PFAS — near industrial sites in northeastern Ohio, military installations (Wright-Patterson AFB, Rickenbacker, LIMA tank plant area)
Arsenic — southern Ohio shale geology; lower risk than western states but worth testing
Atrazine and agricultural pesticides — Ohio's intensive corn and soybean agriculture creates pesticide runoff risk
Iron and manganese — common throughout Ohio, particularly in glacial aquifers and bedrock wells
Hardness and TDS — baseline water chemistry; Ohio water ranges from moderately hard to very hard
Volatile organic compounds (VOCs) — northeastern Ohio industrial corridor (Akron, Canton, Cleveland exurbs)
Common Contamination Risks in Ohio
Nitrate from agriculture — Ohio is one of the nation's most intensively farmed states; shallow wells in agricultural areas face significant nitrate risk, especially in the flat northwestern counties where tile drainage is prevalent
Bacterial contamination from karst and shallow wells — northwest Ohio's limestone karst geology (Findlay Arch region) allows rapid movement of surface contaminants to groundwater; heavy rains can drive bacterial contamination into wells
PFAS from industrial sources — northeastern Ohio has a dense industrial history; PFAS contamination from manufacturing, chrome plating, and firefighting foam use has been documented in several communities
Radon — Ohio's glacial till and bedrock geology produces elevated radon; while primarily an indoor air concern, wells can be a secondary source of radon exposure in some areas
Agricultural pesticides and herbicides — atrazine, acetochlor, and metolachlor are commonly detected in Ohio groundwater near corn and soybean operations
Lead from older well components — Ohio's older rural housing stock frequently has lead-containing well pump fittings, pressure tanks, and galvanized pipes that can leach lead
Legacy industrial contamination — the Mahoning Valley (Youngstown), the Rubber Capital (Akron), and other northeastern Ohio industrial areas have documented groundwater contamination plumes affecting some private wells
Contaminant Guides Relevant to OH 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
pH
Water Quality Indicators
EPA limit: 6.5–8.5 (secondary standard)
Find a Certified Lab in Ohio
Use the Ohio state-certified laboratory program to find accredited labs for private well testing. Always verify current certification before submitting samples.
OH Certified Lab Directory ↗Ohio 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
OH Certified Labs ↗EPA guidance
EPA Private Wells Program ↗State lab directory
OH Certified Labs ↗Minimum Annual Tests
Plus state-specific contaminants listed above
Other State Guides