Well water in Franklin County, Washington
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Testing strongly recommended
tested well samples in Franklin County exceeded the EPA limit for nitrate (10 mg/L), based on public data from USGS Water Quality Portal.
3,225 test results across 15 contaminants from at least 298 wells, 1942 to 2025; nitrate has the most at 882. Data refreshed September 15, 2026.
Compiled by Nick at Well Water Nerd from public records. How these pages are built
An estimated 11,824 people in Franklin County get their drinking water from a private well, per USGS 2015 county water use. That is about 13% of residents.
Separately, the USGS national arsenic model estimates that 27% of the 11,824 people on private wells in Franklin County draw water above 10 ug/L (the model's range is 22% to 34%), from geology and well depth rather than local tests.
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 |
|---|---|---|---|---|---|---|
| Nitrate 1942 to 2025 | 882 | 91% | 6.81 | 266 | 10 mg/L EPA limit | |
| Uranium 2002 to 2025 | 96 | 100% | 9.71 | 68.7 | 30 ug/L EPA limit | |
| Arsenic 1983 to 2025 | 100 | 100% | 4.1 | 17.7 | 10 ug/L EPA limit | |
| Fluoride 1942 to 2025 | 378 | 99% | 0.515 | 4.7 | 4 mg/L EPA limit | |
| Copper 1967 to 2025 | 106 | 71% | 0.001 | 0.14 | 1.3 mg/L EPA limit | |
| Lead 1970 to 2025 | 105 | 50% | 0 | 1.45 | 15 ug/L EPA limit | |
| Radium (226 + 228) 2004 to 2016 | 32 | 66% | 0.088 | 1 | 5 pCi/L EPA limit | |
| E. coli 2002 to 2016 | 18 | 0% | 0 | 0 | 0 MPN/100mL EPA limit | |
| PFOA 2023 to 2024 | 12 | 0% | 0 | 0 | 4 ng/L EPA limit | |
| PFOS 2023 to 2024 | 12 | 17% | 0 | 3.9 | 4 ng/L EPA limit | |
| Chloride 1942 to 2025 | no limit | 486 | 100% | 22 | 330 | 250 mg/L nuisance level |
| Sodium 1942 to 2025 | no limit | 380 | 100% | 43 | 250 | 20 mg/L health guideline |
| Iron 1942 to 2025 | no limit | 299 | 63% | 4 | 1,200 | 300 ug/L nuisance level |
| Manganese 1962 to 2025 | no limit | 263 | 60% | 0 | 1,700 | 300 ug/L health guideline |
| Radon 1993 to 2016 | no limit | 56 | 100% | 515 | 4,000 | 2,000 pCi/L health guideline |
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 | 33%682 samples | 49%94 samples | 40%72 samples | 38%34 samples |
| Fluoride | 1%278 samples | 0%47 samples | 0%36 samples | 0%17 samples |
| Copper | 0%10 samples | 0%43 samples | 0%36 samples | 0%17 samples |
| Uranium | n/a | 19%43 samples | 11%36 samples | 18%17 samples |
| Arsenic | n/a | 12%43 samples | 17%36 samples | 18%17 samples |
| Lead | n/a | 0%43 samples | 0%36 samples | 0%17 samples |
Uranium above the limit in Franklin County fell from 19% of 43 samples in the 2000s to 11% of 36 in the 2010s.
Arsenic above the limit in Franklin County rose from 12% of 43 samples in the 2000s to 17% of 36 in the 2010s.
Nitrate, fluoride, copper, lead 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 addressWhat this means
The contaminants most often above their limit here are nitrate (36% of 882 samples), uranium (16% of 96 samples), and arsenic (14% of 100 samples). A well next door can differ sharply from yours because bedrock fractures, well depth and plumbing all matter, so these rates describe the area, not your tap.
Chloride, Iron, and Manganese 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 Franklin County
- 1Nitrate36% of 882 local samples were above the limit.
- 2Uranium16% of 96 local samples were above the limit.
- 3Arsenic14% of 100 local samples were above the limit.
- 4Fluoride1% of 378 local samples were above the limit.
- 5Coliform bacteriaRecommended for every private well, every year.
- 6RadonMedian local reading is 515 pCi/L.
- 7ChlorideDetected in 100% of local samples.
- 8Volatile organic compounds (VOCs)7 reported spills and releases on record locally.
Test your Franklin County well for nitrate, uranium and arsenic
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 Washington: 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
1,692 domestic wells in Franklin County are on record with the state since 1993. the typical well is 202 feet deep (one in ten goes past 526 feet).
In a typical Franklin County well, the median yield is 75 gallons per minute.
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 Ecology well report search and choose Water Well.
- It lists depth, casing, static water level, the yield test and the driller.
Washington has required well reports since 1971; reports are located only to the quarter-quarter section, so check the address on the scan.
The rock under Franklin County
Columbia Plateau basin-fill aquifers
Unconsolidated sand and gravel. Wells in sand and gravel are usually shallow and productive, and they recharge quickly from the surface. That makes them the most exposed to nitrate, bacteria and anything spilled nearby, and the least likely to carry arsenic or radon from the rock.
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 Washington
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.
- Drinking Water, Washington State Department of Health
- Environmental lab accreditation, Washington State Department of Ecology
Contamination sources on record in Franklin County
Washington Ecology facility interactions records 7 reported spills and releases in Franklin County, among 499 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.
- 7
- reported spills and releasesMost spills are fuel; a few are solvents or chemicals that reach the water table.
- 465
- other remediation projects
- 27
- other solid waste facilities
Treatment that fits the local profile
Nitrate
Point-of-use reverse osmosis; Anion exchange; Distillation
Uranium
Point-of-use reverse osmosis; Anion exchange; Whole-house anion exchange
Arsenic
Point-of-use reverse osmosis; Adsorptive media (iron-based) whole-house; Anion exchange
Fluoride
Point-of-use reverse osmosis; Activated alumina; Distillation
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 nitrate
Under-sink reverse osmosis system
under-sink or countertop, about $300
Look for NSF/ANSI 58 certification listing the contaminant you need removed.
For nitrate
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 uranium
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.
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 202 feet deep, based on 1,692 wells reported to the state since 1993. One in ten is deeper than 526 feet.
Is there arsenic in well water in Franklin County?
Arsenic was detected in 100% of 100 public well samples in Franklin County, and 14% 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 high is radon in well water in Franklin County?
The median radon level across 56 public samples in Franklin County was 515 pCi/L, with a high of 4,000 pCi/L. New Hampshire recommends treatment above 2,000 pCi/L.
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 Washington dataset as CSV, every county and town, with the sources named.
Sources
- USGS Water Quality Portal: 3,225 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.
- USGS national arsenic model (Ayotte 2017): estimated share of 11,824 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.
- Washington Ecology well construction reports: 1,695 well records in Franklin County, 1,692 domestic. Well construction reports filed with the Washington State Department of Ecology, water wells only, located at the quarter-quarter section. Only aggregates are shown; owner names and addresses are never stored. Retrieved September 17, 2026.
- Washington Ecology facility interactions: 499 regulated sites located in Franklin County. Toxics cleanup sites, spills and solid waste facilities from the Washington State Department of Ecology Facility/Site register. 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.