Well water in Franklin County, Missouri

In Franklin County, 2% of 48 tested well samples exceeded the EPA limit for lead (15 ug/L), based on public data from USGS Water Quality Portal.

101 private wells tested 2010 to 2023 in state summaries; 646 test results across 13 contaminants from at least 53 wells, 1946 to 2016; nitrate has the most at 136. Data refreshed September 15, 2026.

Compiled by Nick at Well Water Nerd from public records. How these pages are built

Missouri does not require private well testing, so these are samples homeowners chose to send to the state lab, often after a problem; shares above the limit run higher than a random survey would find.

An estimated 40,586 people in Franklin County get their drinking water from a private well, per USGS 2015 county water use. That is about 40% of residents.

Separately, the USGS national arsenic model estimates that 1% of the 40,586 people on private wells in Franklin County draw water above 10 ug/L (the model's range is <1% to 1%), from geology and well depth rather than local tests.

What homeowner tests found

Missouri DHSS private well sampling summaries: private wells tested and reported to the state, 2010 to 2023. Shares are against the level the state applies to each contaminant, named in the last column; several are stricter than EPA.

Contaminant	Above state level	Wells tested	State level
Iron	9%	43	300 ug/L
Lead	6%	101	15 ug/L
Arsenic	5%	38	10 ug/L
Chloride	2%	45	250 mg/L
Nitrate	0%	48	10 mg/L
Fluoride	0%	46	4 mg/L
Uranium	0%	38	30 ug/L

What individual samples found

Each row summarizes every public sample for that contaminant inside Franklin County. Above limit means above the EPA maximum contaminant level; where EPA has no enforceable limit, the row shows a health guideline or nuisance level instead.

Contaminant	Above limit	Samples	Detected	Median	Highest	Limit
Lead 1990 to 2016	2%	48	25%	0	20	15 ug/L EPA limit
Nitrate 1949 to 2016	1%	136	90%	0.257	22.3	10 mg/L EPA limit
Fluoride 1954 to 2016	0%	71	96%	0.18	0.4	4 mg/L EPA limit
Copper 1990 to 2016	0%	48	23%	0	0.008	1.3 mg/L EPA limit
Arsenic 1993 to 2016	0%	39	49%	0	10	10 ug/L EPA limit
Chloride 1946 to 2016	no limit	79	100%	6.3	240	250 mg/L nuisance level
Iron 1946 to 2016	no limit	79	86%	40	13,100	300 ug/L nuisance level
Sodium 1963 to 2016	no limit	69	100%	14	120	20 mg/L health guideline
Manganese 1954 to 2016	no limit	65	80%	2	1,600	300 ug/L health guideline

Sampled fewer than 10 times, too few to summarize: Radium (226 + 228) (4), Uranium (3), E. coli (2), Radon (3).

Over time

Share of samples above the limit by period. A cell needs ten samples to show; a comparison needs twenty in each period. Later periods sample fewer wells, and often the ones already known to have a problem.

Contaminant	before 2000	2000s	2010s	2020s
Nitrate	1%70 samples	2%62 samples	n/a	n/a
Fluoride	0%38 samples	0%31 samples	n/a	n/a
Lead	7%15 samples	0%31 samples	n/a	n/a
Copper	0%15 samples	0%31 samples	n/a	n/a

Nitrate, fluoride have held within a few points between the two most recent periods with enough samples.

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 address

What this means

Among homeowners in Franklin County who sent a sample to the state lab, the health-based limits most often exceeded were lead (6% of 101 wells) and arsenic (5% of 38 wells). These are ordinary wells tested by their owners, so the shares are the best available picture of a typical well here, with one caveat: people test more often when they suspect a problem.

What to test for in Franklin County

1
Lead
6% of 101 local wells tested were above the EPA limit.
2
Arsenic
5% of 38 local wells tested were above the EPA limit.
3
Nitrate
1% of 136 local samples were above the limit.
4
Coliform bacteria
Recommended for every private well, every year.
5
Radon
Median local reading is 138 pCi/L.
6
Iron
9% of 43 local wells tested were above the EPA secondary standard.
7
Chloride
2% of 45 local wells tested were above the EPA secondary standard.
8
Fluoride
Detected in 96% of local samples.
9
Volatile organic compounds (VOCs)
138 hazardous waste sites on record locally.
10
Metals panel
138 hazardous waste sites on record locally.

Test your Franklin County well for lead, arsenic and nitrate

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 $209 Already 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 Missouri: certified labs, state programs and prices.

Already have results back? Get your lab report read against the Franklin County numbers, $29. Every line explained, ranked by what matters, with the fix for each.

Wells in Franklin County

7,803 domestic wells in Franklin County are on record with the state since 1986. the typical well is 306 feet deep (one in ten goes past 426 feet).

In a typical Franklin County well, the median yield is 25 gallons per minute, <1% of wells yield under 3 gallons per minute and usually need a storage tank.

1,049

1980s

2,841

1990s

2,429

2000s

1,093

2010s

369

2020s

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 Missouri DNR WIMS and choose Water Well.
The certification record lists total depth, casing length, static water level, yield and the driller.

Missouri has required certification of new private wells since 1987, so a well drilled before then usually has no record.

The rock under Franklin 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 Missouri

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 Drinking Water, Missouri DHSS
Certified Laboratories, Missouri DNR

Contamination sources on record in Franklin County

Missouri DNR records 138 hazardous waste sites in Franklin County, among 293 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.

138: hazardous waste sitesSolvents, degreasers and metals from industrial sites can travel far in fractured bedrock.
141: registered underground storage tank sitesRegistered tanks are regulated and inspected; they matter most when they are old or near a shallow well.
13: lined landfills and transfer facilities
1: other solid waste facility

Treatment that fits the local profile

Lead

Point-of-use reverse osmosis; Certified lead-removal carbon filter; Neutralizing filter to raise pH and stop leaching

Arsenic

Point-of-use reverse osmosis; Adsorptive media (iron-based) whole-house; Anion exchange

Iron

Oxidizing filter whole-house; Water softener (low levels); Aeration plus filtration

Nitrate

Point-of-use reverse osmosis; Anion exchange; Distillation

Manganese

Oxidizing filter (greensand, birm) whole-house; Water softener (low levels); Point-of-use reverse osmosis

Systems we would look at first

Some links below are affiliate links. If you buy through one, the merchant pays us a commission at no extra cost to you. It does not change which products we list or what the data says.

For lead

Under-sink reverse osmosis system

under-sink or countertop, about $300

Look for NSF/ANSI 58 certification listing the contaminant you need removed.

For lead

Acid neutralizing filter

whole-house, at the point of entry, about $1,200

Raises pH so plumbing stops leaching lead and copper.

For lead

Aquasana SmartFlow reverse osmosis

under-sink or countertop, about $225

Certified to NSF/ANSI 58 and 53 to reduce arsenic (96%, pentavalent), fluoride (90%), lead (99%), nitrate, nitrite and PFOA/PFOS at the kitchen tap, with a remineralizer.

For arsenic

Whole-house arsenic and uranium filter

whole-house, at the point of entry, about $2,500

Adsorptive iron-based media; sized to your well yield.

For iron

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 Franklin County

No water treatment company serves Franklin 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 Franklin County, and you get an email naming it first.

Common questions

How deep are wells in Franklin County?

The typical domestic well in Franklin County is 306 feet deep, based on 7,803 wells reported to the state since 1986. One in ten is deeper than 426 feet.

Is there arsenic in well water in Franklin County?

Arsenic was detected in 49% of 39 public well samples in Franklin County, and 0% were above the EPA limit of 10 ug/L. Arsenic has no taste or smell; a lab test is the only way to know your level.

How often should I test a private well in Franklin 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.

Counties near Franklin 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 Missouri dataset as CSV, every county and town, with the sources named.

Sources

USGS Water Quality Portal: 646 samples in Franklin 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.
Missouri DHSS private well sampling summaries: summaries for 7 contaminants in Franklin County, up to 101 wells each. County summaries of private well samples analyzed by the Missouri State Public Health Laboratory, 2010 to 2023, published by the Missouri Department of Health and Senior Services. Counts are samples, not distinct wells. Shares are against the EPA maximum contaminant level, or the EPA secondary standard for chloride and iron. Counties with fewer than 20 samples are flagged unreliable by DHSS and are kept here with their counts so the threshold rule can judge them. Barium, sulfate and zinc layers exist but have no contaminant page yet. Retrieved September 15, 2026.
USGS national arsenic model (Ayotte 2017): estimated share of 40,586 people on private wells in Franklin 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.
Missouri DNR certified well records: 10,496 well records in Franklin County, 7,803 domestic. Well certification records from the Missouri Department of Natural Resources Wellhead Information Management System (WIMS), published through MSDIS. Only aggregates are shown; owner names and addresses are never stored. Retrieved September 15, 2026.
Missouri DNR regulated sites: 293 regulated sites located in Franklin County. Permitted solid waste facilities, and leaking tank, underground tank and hazardous waste sites from the historical CARES potential contaminant site inventory, Missouri Department of Natural Resources. Retrieved September 15, 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.