Well water in Defiance County, Ohio
No public well test results have been compiled for Defiance County yet. The USGS national arsenic model estimates that 40% of the 13,695 people on private wells there draw water with arsenic above 10 ug/L, the EPA limit, based on geology, well depth and land use rather than local tests.
The strongest signal is coliform bacteria: Recommended for every private well, every year, too few samples to carry the headline but first on the test list below.
38 test results across 10 contaminants from at least 3 wells, 2012 to 2016; arsenic has the most at 4. Data refreshed September 15, 2026.
Compiled by Nick at Well Water Nerd from public records. How these pages are built
Data confidence: estimate. No state program or federal monitoring data for Defiance County has been compiled here yet, so the arsenic figure is the USGS national model, not a measurement. Treat a high estimate as a reason to test, not as your well's number. Measured results are added as states publish them.
An estimated 13,695 people in Defiance County get their drinking water from a private well, per USGS 2015 county water use. That is about 36% of residents.
Closer than the county
See the sampled wells near your address
The same records, drawn around one point: which wells within a few miles were sampled and what they found, how deep the wells next to you were drilled, and any leaking tank or cleanup site within a mile.
Check my addressWhat this means
Among contaminants with a federal limit, no tested sample in Defiance County came back above it. That is reassuring, but sampling is uneven: wells that were never tested are not in this data.
Manganese, Chloride, and Iron are widespread in local groundwater. They are mainly a staining and taste problem, but high manganese also carries a health advisory for infants.
What to test for in Defiance County
- 1Coliform bacteriaRecommended for every private well, every year.
- 2NitrateRecommended for every private well, especially near farms or septic systems.
- 3FluorideDetected in 100% of local samples.
- 4ChlorideDetected in 100% of local samples.
- 5IronDetected in 100% of local samples.
- 6ManganeseDetected in 75% of local samples.
- 7Volatile organic compounds (VOCs)178 leaking underground storage tank sites on record locally.
- 8Metals panel7 hazardous waste sites on record locally.
Test your Defiance County well for coliform bacteria, nitrate and fluoride
Certified lab analysis of your own tap water, bottles and prepaid return shipping included. The Essential well panel covers arsenic, uranium, nitrate, lead, copper, manganese, iron, sodium and bacteria; radon and PFAS are add-ons.
Order the Tap Score well water test kit, from $209Already tested? Upload the report
Just want bacteria checked first? Tap Score coliform and E. coli test, $99. Coliform and E. coli are the tests every well needs every year.
Want a quick look before paying for a lab? Home well water test strips on Amazon check hardness, iron, pH and nitrate in minutes. They are a screen, not a result: arsenic, bacteria, uranium and PFAS need a certified lab.
Affiliate links: the merchant pays us a commission and the price is the same for you. It does not change what the data above says. As an Amazon Associate we earn from qualifying purchases.
Where to get a well tested in Ohio: certified labs, state programs and prices.
Already have results back? Get your lab report read against the Defiance County numbers, $29. Every line explained, ranked by what matters, with the fix for each.
Wells in Defiance County
2,217 domestic wells in Defiance County are on record with the state since 1970. 46% are drilled into bedrock, and the typical well is 87 feet deep (one in ten goes past 142 feet).
In a typical Defiance County well, bedrock starts about 72 feet down, the median yield is 18 gallons per minute, 6% of wells yield under 3 gallons per minute and usually need a storage tank.
Find your own well's report
The state keeps the driller's report for most wells drilled since 1984. It tells you how deep your well is, where bedrock starts, and how much water it makes, which decides what treatment can work.
- Open ODNR water well log search and choose Water Well.
- The log lists depth, depth to bedrock, casing, static water level, the pump test and the driller.
Ohio has required well logs since 1948, so most drilled wells have one.
The rock under Defiance County
Not a principal aquifer
The USGS map places this area outside any principal aquifer, which usually means wells here draw from fractured bedrock or thin local deposits rather than a large regional aquifer. Bedrock wells of that kind are where arsenic, radon and uranium turn up, and yields vary from well to well.
Classification from the USGS Principal Aquifers of the United States (national map, 2003 edition, GIS release 2015), read at the county centroid. A single well can sit in a different unit, especially near a boundary.
Official help in Ohio
Two places to start that are not selling anything: the state program that answers private well questions, and its list of labs certified to run drinking water tests. A certified lab is the difference between a result you can act on and a number.
- Private Water Systems Program, Ohio Department of Health
- Laboratory Certification, Ohio EPA
Contamination sources on record in Defiance County
Ohio EPA records 178 leaking underground storage tank sites and 7 hazardous waste sites in Defiance County, among 191 regulated sites in total. Groundwater does not follow property lines, so a well within a few hundred feet of one of these is worth testing for what that site could release.
- 178
- leaking underground storage tank sitesGasoline and heating oil that leaked from tanks move through groundwater as benzene, MTBE and other volatile organic compounds.
- 7
- hazardous waste sitesSolvents, degreasers and metals from industrial sites can travel far in fractured bedrock.
- 3
- lined landfills and transfer facilities
- 3
- other remediation projects
Treatment that fits the local profile
Iron
Oxidizing filter whole-house; Water softener (low levels); Aeration plus filtration
Manganese
Oxidizing filter (greensand, birm) whole-house; Water softener (low levels); Point-of-use reverse osmosis
Systems we would look at first
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For manganese
Iron and manganese oxidizing filter
whole-house, at the point of entry, about $1,800
Air-injection or greensand media; fixes staining at the source.
Free, no obligation
Get on the list for a free in-home water test in Defiance County
No water treatment company serves Defiance County through Well Water Nerd yet. We are signing licensed companies on county by county: they test at your tap for free, walk you through the numbers, and quote treatment only if something needs fixing. Leave your details and you are first in line. Nothing is shared until a company joins for Defiance County, and you get an email naming it first.
Common questions
How deep are wells in Defiance County?
The typical domestic well in Defiance County is 87 feet deep, based on 2,217 wells reported to the state since 1970. One in ten is deeper than 142 feet. 46% are drilled into bedrock.
How often should I test a private well in Defiance County?
Test for bacteria and nitrate every year. Test once for arsenic, uranium, radon, fluoride, manganese and PFAS, then again every three to five years or after any change in taste, color, or plumbing.
Towns in Defiance County
12 towns have fewer than 30 public samples and are included in the Defiance County totals above rather than shown separately: Adams township, Defiance township, Delaware township, Farmer township, Hicksville township, Highland township, Mark township, Milford township, Noble township, Richland township, Tiffin township, Washington township.
Counties near Defiance County
Closest first. Groundwater does not stop at a line on a map, so the next county over is a fair second opinion.
Want the numbers themselves? Download the Ohio dataset as CSV, every county and town, with the sources named.
Sources
- USGS Water Quality Portal: 38 samples in Defiance County. Data from the Water Quality Portal, a service of USGS, EPA and USDA; groundwater samples collected by USGS and cooperators. Retrieved September 3, 2026.
- USGS national arsenic model (Ayotte 2017): estimated share of 13,695 people on private wells in Defiance County above 10 ug/L of arsenic, from geology, well depth and land use. County estimates of domestic well users with arsenic above 10 ug/L from the USGS national logistic regression model (Ayotte, Medalie and Qi, 2017), with private well population from the USGS 2015 county water-use compilation (Dieter and others, 2018). Retrieved September 15, 2026.
- Ohio DNR water well logs: 2,598 well records in Defiance County, 2,217 domestic. Water well logs filed with the Ohio Department of Natural Resources Division of Water Resources since 1948. Only aggregates are shown; owner names and addresses are never stored. Retrieved September 17, 2026.
- Ohio EPA regulated sites: 191 regulated sites located in Defiance County. Remediation sites, leaking underground storage tank releases (BUSTR) and landfills from the Ohio Environmental Protection Agency and the Division of State Fire Marshal. Retrieved September 17, 2026.
Non-detects count as samples and are treated as zero when computing medians. Exactly at the limit counts as not above it. A sample belongs to the town containing the well's reported coordinates.