Health problems are rare in tested Hillsborough County wells.
All 7 health checks came back rare here.
From 189 wells tested in Hillsborough County since 2000; your own well needs its own test. How to read this
Rare: under 5%Worth checking: 5 to 15%Widespread: 15%+
Lab results: Water Quality Portal (USGS and EPA)
Who drinks from a well here
About 1 in 18 people 81,928 people
Nobody else tests these wells. Only you do.
People on wells: EPA researchers' 2020 estimate
Radon risk (a gas from rock)
Possible here. A home air test is inexpensive.
Radon zones: EPA map
Here's how Hillsborough County compares with Florida and the counties around it.
Each result puts Hillsborough County next to the 5 counties that border it, on the chart's 0 to 50% scale.
All 7 health checks are rare in Hillsborough County.
Arsenic4 of 98 wells over
Nitrate4 of 121 wells over
Too few tested to show: Hardee.
Radon in water1 of 40 wells over
Lead2 of 98 wells over
Manganese2 of 159 wells over
Fluoride0 of 169 wells over
Uranium0 of 49 wells over
Too few tested to show: Hardee, Manatee, Pinellas.
Coliform bacteria turned up in 20 of 44 tested Hillsborough County wells, so test for it every year.
Coliform bacteria20 of 44 wells had it
Most of Florida's bacteria results come from shallow monitoring-network wells, so they aren't a guide to household wells.
E. coli3 of 25 wells had it
Too few tested to show: Hardee, Pinellas.
E. coli means human or animal waste is getting in, so if a test of your Hillsborough County well finds it, boil drinking water until the well is fixed.
Iron reached staining levels in 76 of 174 tested wells, and it isn't a health risk.
Iron stains76 of 174 wells had it
About 5 in 10 of the 189 wells tested in Hillsborough County have a test from 2020 or later.
With 102 wells tested since 2020, age matters less here than who did the testing and why.
Most Hillsborough County wells in these records were tested for research or because someone suspected a problem, which can push the shares above what a typical home well would show (how we read the numbers).
One mail-in lab test covers the 3 things to check in Hillsborough County.
- Bacteria
- Nitrate
- Arsenic
What Florida offers well owners
- Free testingSome county health departments may test for certain toxic substances free of charge. See the program
- Certified labsFlorida's list of certified labs
- Well recordsWe didn't find an online search.
- New wellsNo statewide rule, but Hillsborough County requires testing of new or repaired wells under a local rule.
Here's what we know about radon and PFAS in Hillsborough County.
Hillsborough County is in the EPA's middle radon zone. An indoor air test is cheap and tells you whether to look at your water. Radon guide
Between 2023 and 2025 the EPA had 12 town water systems in Hillsborough County test for PFAS. 9 of them had at least one test above 4 ng/L, the new EPA limit for PFOA and PFOS. The highest single result was 25 ng/L of PFOS. No well in Hillsborough County has public PFAS results, so the town systems are the best clue to what's in the groundwater nearby. PFAS guide
Radon zones: EPA Map of Radon Zones. PFAS: EPA tests of town water systems, 2023 to 2025
Questions people ask about well water in Hillsborough County
Is well water in Hillsborough County safe to drink?
Most tested wells in Hillsborough County came in under the limits. Of 7 health checks with enough tests, arsenic came closest, at 4 of 98 wells over. Every well is different, so test yours for bacteria, nitrate and arsenic.
Can I get my well tested for free in Hillsborough County?
Some county health departments may test for certain toxic substances free of charge. If not, use a lab Florida has certified for drinking water. Ask for bacteria, nitrate and arsenic, the tests that matter most in Hillsborough County.
How does Hillsborough County compare with the counties around it?
For arsenic, the share of tested wells over the limit: 1 of the 5 neighboring counties with data had a higher share than Hillsborough County, at 4%. Pinellas had the most, at 14%. Groundwater doesn't stop at county lines, so Pinellas's 14% is worth knowing about if you live near it.
How often should I test my well in Hillsborough County?
In Hillsborough County, 20 of 44 tested wells had coliform bacteria, so the CDC's advice matters here: test for bacteria and nitrate every year, and right away after a flood, a repair, or any change in taste or smell.
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Where the Hillsborough County numbers come from
- People on wells: 81,928 in Hillsborough County, from EPA estimates built on the 2020 Census (Murray et al.).
- Lab tests: 4,668 well water samples from 189 wells in the Water Quality Portal, run by the USGS and EPA, 2000 to 2026.
- Neighboring counties: the 5 counties that share a border with Hillsborough County, from the Census Bureau's county adjacency file.
- PFAS: EPA tests of 12 town water systems in Hillsborough County under the Fifth Unregulated Contaminant Monitoring Rule, 2023 to 2025.
- Radon: Hillsborough County is zone 2 on the EPA Map of Radon Zones.
- State programs and links: Department of Health, checked November 1, 2026.