Florida well water by county: arsenic and nitrate
Modelled arsenic and nitrate for private-well users in every Florida county, what to test for, and where to find a certified lab. Private wells aren’t covered by the Safe Drinking Water Act.
All 67 counties
- Hillsborough CountyWell users 131,600Arsenic about 1 in 100Nitrate 0.0 mg/L
- Marion CountyWell users 97,000Arsenic about 1 in 100Nitrate 1.3 mg/L
- Duval CountyWell users 89,800Arsenic about 2 in 100Nitrate 0.0 mg/L
- Polk CountyWell users 84,900Arsenic about 1 in 100Nitrate 0.0 mg/L
- Palm Beach CountyWell users 82,000Arsenic about 1 in 100Nitrate 0.0 mg/L
- Pasco CountyWell users 61,300Arsenic about 2 in 100Nitrate 0.1 mg/L
- Orange CountyWell users 58,400Arsenic about 1 in 100Nitrate 0.0 mg/L
- Lake CountyWell users 55,200Arsenic about 1 in 100Nitrate 0.1 mg/L
- Volusia CountyWell users 54,800Arsenic about 1 in 100Nitrate 0.0 mg/L
- Putnam CountyWell users 47,900Arsenic about 2 in 100Nitrate 0.0 mg/L
- Miami-Dade CountyWell users 46,900Arsenic about 3 in 100Nitrate 0.8 mg/L
- St. Lucie CountyWell users 46,000Arsenic about 1 in 100Nitrate 0.0 mg/L
- Citrus CountyWell users 44,200Arsenic about 2 in 100Nitrate 0.1 mg/L
- Lee CountyWell users 43,400Arsenic about 2 in 100Nitrate 0.0 mg/L
- Sarasota CountyWell users 43,000Arsenic about 2 in 100Nitrate 0.0 mg/L
- Alachua CountyWell users 39,300Arsenic about 1 in 100Nitrate 0.5 mg/L
- Brevard CountyWell users 38,100Arsenic about 2 in 100Nitrate 0.0 mg/L
- Bay CountyWell users 36,500Arsenic about 4 in 100Nitrate 0.0 mg/L
- Martin CountyWell users 35,600Arsenic about 2 in 100Nitrate 0.0 mg/L
- Columbia CountyWell users 35,200Arsenic about 1 in 100Nitrate 0.3 mg/L
- Clay CountyWell users 35,200Arsenic about 2 in 100Nitrate 0.0 mg/L
- St. Johns CountyWell users 33,600Arsenic about 2 in 100Nitrate 0.0 mg/L
- Collier CountyWell users 32,100Arsenic about 2 in 100Nitrate 0.0 mg/L
- Nassau CountyWell users 31,700Arsenic about 2 in 100Nitrate 0.0 mg/L
- Jackson CountyWell users 29,900Arsenic about 1 in 100Nitrate 1.7 mg/L
- Suwannee CountyWell users 28,700Arsenic about 2 in 100Nitrate 1.0 mg/L
- Indian River CountyWell users 28,100Arsenic about 2 in 100Nitrate 0.0 mg/L
- Seminole CountyWell users 27,300Arsenic about 1 in 100Nitrate 0.1 mg/L
- Levy CountyWell users 26,300Arsenic about 1 in 100Nitrate 0.4 mg/L
- Leon CountyWell users 24,800Arsenic about 2 in 100Nitrate 0.3 mg/L
- Hernando CountyWell users 23,800Arsenic about 3 in 100Nitrate 0.0 mg/L
- Sumter CountyWell users 22,900Arsenic about 2 in 100Nitrate 0.2 mg/L
- Osceola CountyWell users 22,800Arsenic about 1 in 100Nitrate 0.0 mg/L
- Manatee CountyWell users 20,700Arsenic about 2 in 100Nitrate 0.0 mg/L
- Highlands CountyWell users 19,900Arsenic about 1 in 100Nitrate 0.1 mg/L
- Broward CountyWell users 19,600Arsenic about 2 in 100Nitrate 0.0 mg/L
- Walton CountyWell users 19,300Arsenic about 3 in 100Nitrate 0.1 mg/L
- Baker CountyWell users 18,700Arsenic about 1 in 100Nitrate 0.0 mg/L
- Bradford CountyWell users 16,700Arsenic about 1 in 100Nitrate 0.0 mg/L
- Okeechobee CountyWell users 16,500Arsenic about 1 in 100Nitrate 0.0 mg/L
- Washington CountyWell users 15,600Arsenic about 2 in 100Nitrate 0.2 mg/L
- Gadsden CountyWell users 15,500Arsenic about 2 in 100Nitrate 0.0 mg/L
- Wakulla CountyWell users 14,500Arsenic about 2 in 100Nitrate 0.1 mg/L
- DeSoto CountyWell users 14,400Arsenic about 2 in 100Nitrate 0.0 mg/L
- Gilchrist CountyWell users 13,900Arsenic about 1 in 100Nitrate 1.0 mg/L
- Hardee CountyWell users 13,500Arsenic about 1 in 100Nitrate 0.0 mg/L
- Taylor CountyWell users 13,300Arsenic about 2 in 100Nitrate 0.0 mg/L
- Hendry CountyWell users 12,500Arsenic about 3 in 100Nitrate 0.0 mg/L
- Holmes CountyWell users 12,500Arsenic about 1 in 100Nitrate 0.2 mg/L
- Dixie CountyWell users 11,400Arsenic about 1 in 100Nitrate 0.1 mg/L
- Madison CountyWell users 11,300Arsenic about 2 in 100Nitrate 0.3 mg/L
- Jefferson CountyWell users 10,200Arsenic about 1 in 100Nitrate 0.2 mg/L
- Charlotte CountyWell users 9,500Arsenic about 3 in 100Nitrate 0.0 mg/L
- Calhoun CountyWell users 9,400Arsenic about 2 in 100Nitrate 0.1 mg/L
- Union CountyWell users 9,000Arsenic about 1 in 100Nitrate 0.0 mg/L
- Gulf CountyWell users 8,600Arsenic about 2 in 100Nitrate 0.0 mg/L
- Santa Rosa CountyWell users 8,500Arsenic about 2 in 100Nitrate 0.8 mg/L
- Hamilton CountyWell users 8,200Arsenic about 2 in 100Nitrate 0.2 mg/L
- Okaloosa CountyWell users 8,000Arsenic about 2 in 100Nitrate 0.2 mg/L
- Lafayette CountyWell users 6,900Arsenic about 2 in 100Nitrate 0.2 mg/L
- Pinellas CountyWell users 6,500Arsenic about 3 in 100Nitrate 0.0 mg/L
- Flagler CountyWell users 6,000Arsenic about 1 in 100Nitrate 0.0 mg/L
- Glades CountyWell users 4,800Arsenic about 3 in 100Nitrate 0.0 mg/L
- Liberty CountyWell users 4,600Arsenic about 2 in 100Nitrate 0.0 mg/L
- Escambia CountyWell users 3,300Arsenic about 3 in 100Nitrate 0.8 mg/L
- Franklin CountyWell users 2,500Arsenic about 2 in 100Nitrate 0.0 mg/L
- Monroe CountyWell users 2,000Arsenic about 4 in 100Nitrate 0.0 mg/L
Each mark = 1 in 100 well users the model places above 10 µg/L arsenic (scale 0–10)10 mg/L nitrate: the federal limit (MCL) for public systems
- These figures describe the area, not your well. Only a lab test shows what’s in your water.
- CDC says the Well Water Index figures “do not describe risk to individual wells.” (CDC Tracking Network)
- The arsenic model is better at spotting low-arsenic areas than at confirming high ones.
- Well-user counts are 2010 USGS estimates; tract values are averages over each census tract.
- Total coliform bacteriaEvery year
- NitrateEvery year
- Total dissolved solidsEvery year
- pHEvery year
- ArsenicAsk your local health department
EPA: Private Drinking Water Wells · CDC: Guidelines for Testing Well Water
Use a state-certified lab
Florida Department of Health lists the laboratories certified to test drinking water in Florida.
Screening tells you if something is worth a closer look
A lab result is the number you can act on.
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Lab-certified results
ETR Labs Basic Water Quality Test Kit
ETR Laboratories
50+ substances, including lead, copper, arsenic, nitrate, hardness and coliform bacteria
- Analyzed by Environmental Testing and Research Laboratories (ETR Labs), Leominster, MA · ISO/IEC 17025:2017, ANAB certificate AT-2638
- Turnaround: 2–4 business days after the lab receives it
What it can't tell you: It does not test PFAS, and not every result on the panel falls under the lab's accredited scope.
Screening: quick check, not lab-grade
Watersafe Drinking Water Test Kit
Silver Lake Research
Lead, bacteria, nitrate, copper, iron, chlorine, hardness and pH
- Turnaround: Minutes; the bacteria test can take up to 48 hours
What it can't tell you: Each test gives a yes/no or a rough range, not a lab number, and it cannot detect PFAS or arsenic.
A mail-in kit’s lab is accredited (ISO/IEC 17025) but may not be certified by your state. For a home sale, a loan, or a health-department follow-up, use a state-certified lab.
Florida well water
Sources: CDC Well Water Index (2024) · USGS arsenic and nitrate models · USGS domestic well populations · EPA and CDC testing guidance. Data last updated 2026-10-08. All sources →
How many people use private wells in Florida?
About 1.9 million people across 67 Florida counties, by the USGS 2010 estimate. USGS models place about 32,700 of them in areas where wells are likely to be above the 10 µg/L arsenic limit. These are area estimates, not well results.
Are private wells regulated in Florida?
The quality and safety of drinking water from private domestic wells are not regulated by the Federal Government under the Safe Drinking Water Act nor by most state governments and laws. (EPA) Testing and treatment are the owner's responsibility.
Where can I get my well tested in Florida?
Florida Department of Health keeps the list of laboratories certified to test drinking water in Florida. Only use laboratories that are certified to do drinking water testing. (EPA)