Health problems are rare in tested St. Johns County wells.

All 5 health checks came back rare here.

From 59 wells tested in St. Johns County since 2003; your own well needs its own test. How to read this

Tested wells over the limit St. JohnsFlorida

Lead2%1 of 54 Arsenic2%1 of 57 Manganese2%1 of 59 Nitrate0%0 of 46 Fluoride0%0 of 27

GermsTest every year, whatever the chart says

Coliform bacteria48%10 of 21 E. coli8%1 of 13

StainsNot a health risk

Iron stains44%26 of 59

Not charted, because fewer than 10 wells were tested: uranium (1), radon (1).

Rare: under 5%Worth checking: 5 to 15%Widespread: 15%+

Lab results: Water Quality Portal (USGS and EPA)

Show bacteria and iron

Who drinks from a well here

1 in 7 people 41,186 people

Nobody else tests these wells. Only you do.

People on wells: EPA researchers' 2020 estimate

Radon risk (a gas from rock)

LowMiddleHigh

Less likely, but the EPA still says test your air.

Radon zones: EPA map

Here's how St. Johns County compares with Florida and the counties around it.

Each result puts St. Johns County next to the 4 counties that border it, on the chart's 0 to 50% scale.

All 5 health checks are rare in St. Johns County.

Lead1 of 54 wells over

1 of 54 wells tested here from 2005 to 2025 was over the EPA action level of 15 µg/L, against about 1 in 9 across Florida. That's a bigger share than in 33 of the 63 other Florida counties with 10 or more tested wells.

St. Johns and its neighbors

Flagler3%

St. Johns2%

Clay1%

Duval0%

Putnam0%

Lead guide

Arsenic1 of 57 wells over

1 of 57 wells tested here from 2005 to 2025 was over the EPA limit of 10 µg/L, against about 1 in 9 across Florida. That's a smaller share than in 36 of the 63 other Florida counties with 10 or more tested wells.

St. Johns and its neighbors

Clay8%

Flagler3%

Putnam2%

St. Johns2%

Duval1%

Arsenic guide

Manganese1 of 59 wells over

1 of 59 wells tested here from 2005 to 2025 was over the EPA health advisory of 0.3 mg/L, against under 1 in 100 across Florida. At least half the results were too low for the lab to measure, and the top 1 in 10 were 0.11 mg/L or more. That's a bigger share than in 55 of the 63 other Florida counties with 10 or more tested wells.

St. Johns and its neighbors

Duval3%

St. Johns2%

Clay1%

Flagler0%

Putnam0%

Manganese guide

Nitrate0 of 46 wells over

None of the 46 wells tested here from 2003 to 2026 were over the EPA limit of 10 mg/L, against about 1 in 32 across Florida. At least half the results were too low for the lab to measure, and the top 1 in 10 were 0.045 mg/L or more. St. Johns County had none, while 25 of the 59 other Florida counties with 10 or more tested wells had at least one.

St. Johns and its neighbors

Duval23%

Clay0%

Flagler0%

Putnam0%

St. Johns0%

Nitrate guide

Fluoride0 of 27 wells over

None of the 27 wells tested here from 2003 to 2026 were over the EPA limit of 4 mg/L, against under 1 in 50 across Florida. Half the results were under 0.1 mg/L, and the top 1 in 10 were 1.2 mg/L or more. St. Johns County had none, while 16 of the 63 other Florida counties with 10 or more tested wells had at least one.

St. Johns and its neighbors

Clay0%

Duval0%

Flagler0%

Putnam0%

St. Johns0%

Too few St. Johns County wells were tested for these 2.

Uranium1 well tested

Only 1 well here was tested in 2019, too few to say how common it is. Across Florida it's under 1 in 100.

Uranium guide

Radon in water1 well tested

Only 1 well here was tested in 2019, too few to say how common it is. Across Florida it's about 1 in 45.

Radon guide

Coliform bacteria turned up in 10 of 21 tested St. Johns County wells, so test for it every year.

Coliform bacteria10 of 21 wells had it

About 5 in 10 wells tested here from 2013 to 2026 had coliform bacteria, against about 5 in 10 across Florida.

St. Johns and its neighbors

St. Johns48%

Duval44%

Flagler44%

Putnam44%

Clay29%

Most of Florida's bacteria results come from shallow monitoring-network wells, so they aren't a guide to household wells.

Bacteria guide

E. coli1 of 13 wells had it

1 of 13 wells tested here from 2019 to 2026 had E. coli, against about 1 in 12 across Florida.

St. Johns and its neighbors

St. Johns8%

Clay0%

Flagler0%

Too few tested to show: Duval, Putnam.

E. coli means human or animal waste is getting in, so if a test of your St. Johns County well finds it, boil drinking water until the well is fixed.

Bacteria guide

Iron reached staining levels in 26 of 59 tested wells, and it isn't a health risk.

Iron stains26 of 59 wells had it

About 4 in 10 wells tested here from 2003 to 2025 had enough iron to stain (0.3 mg/L), against about 4 in 10 across Florida.

St. Johns and its neighbors

Flagler56%

Putnam51%

Clay51%

St. Johns44%

Duval39%

Iron guide

About 7 in 10 of the 59 wells tested in St. Johns County have a test from 2020 or later.

12 wells had a test in the 2000s, 42 in the 2010s and 41 since 2020.

With 41 wells tested since 2020, age matters less here than who did the testing and why.

Most St. Johns 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 St. Johns 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. We didn't find a local rule for St. Johns County, so ask its health department.

Here's what we know about radon and PFAS in St. Johns County.

St. Johns County is in the EPA's lowest radon zone, so radon from well water is unlikely to be a problem. Radon guide

Between 2023 and 2025 the EPA had 8 town water systems in St. Johns County test for PFAS. 1 found some PFAS, all below the new limits. No well in St. Johns 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

Next door to St. Johns County

Duval Clay Putnam

Elsewhere in Florida

Marion Brevard Volusia Hillsborough Lake

All of Florida

Questions people ask about well water in St. Johns County

Is well water in St. Johns County safe to drink?

Most tested wells in St. Johns County came in under the limits. Of 5 health checks with enough tests, lead came closest, at 1 of 54 wells over. Every well is different, so test yours for bacteria, nitrate and arsenic.

Can I get my well tested for free in St. Johns 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 St. Johns County.

How does St. Johns County compare with the counties around it?

For lead, the share of tested wells over the limit: 1 of the 4 neighboring counties with data had a higher share than St. Johns County, at 2%. Flagler had the most, at 3%. Groundwater doesn't stop at county lines, so Flagler's 3% is worth knowing about if you live near it.

How often should I test my well in St. Johns County?

In St. Johns County, 10 of 21 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.

By the Tested Water teamData from the USGS, EPA and Department of HealthUpdated November 8, 2026

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Where the St. Johns County numbers come from

People on wells: 41,186 in St. Johns County, from EPA estimates built on the 2020 Census (Murray et al.).
Lab tests: 1,789 well water samples from 59 wells in the Water Quality Portal, run by the USGS and EPA, 2003 to 2026.
Neighboring counties: the 4 counties that share a border with St. Johns County, from the Census Bureau's county adjacency file.
PFAS: EPA tests of 8 town water systems in St. Johns County under the Fifth Unregulated Contaminant Monitoring Rule, 2023 to 2025.
Radon: St. Johns County is zone 3 on the EPA Map of Radon Zones.
State programs and links: Department of Health, checked November 1, 2026.

Download this county's data (CSV)How we read these numbers Report an error