Arsenic is widespread in Clark County wells.

1 widespread, 1 worth checking, 4 rare out of 6 health checks.

From 40 wells tested in Clark County since 2003; your own well needs its own test. How to read this

Tested wells over the limit ClarkNevada

Arsenic28%8 of 29 Fluoride7%2 of 28 Manganese4%1 of 28 Uranium0%0 of 27 Nitrate0%0 of 35 Lead0%0 of 28

GermsTest every year, whatever the chart says

Coliform bacteria17%1 of 6 E. coli17%1 of 6

StainsNot a health risk

Iron stains18%5 of 28

Not charted, because fewer than 10 wells were tested: radon (5).

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

About 1 in 78 people 28,919 people

Nobody else tests these wells. Only you do.

People on wells: EPA researchers' 2020 estimate

How deep wells go here

Deep wells: fewer surface germs, more minerals from the rock.

Well depths: US Groundwater Well Database

Radon risk (a gas from rock)

LowMiddleHigh

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

Radon zones: EPA map

Here's how Clark County compares with Nevada and the counties around it.

Each result puts Clark County next to the 5 counties that border it, on the chart's 0 to 50% scale.

This one is widespread in Clark County wells.

Arsenic8 of 29 wells over

About 3 in 10 wells tested here from 2004 to 2019 were over the EPA limit of 10 µg/L, against about 6 in 10 across Nevada. Half the results were under 2.7 µg/L, and the top 1 in 10 were 17 µg/L or more. That's a bigger share than in 3 of the 6 other Nevada counties with 10 or more tested wells, leaving out 2 counties whose results are likely overstated.

Clark and its neighbors

Clark28%

San Bernardino, CA24%

Inyo, CA17%

Mohave, AZ16%

Too few tested to show: Lincoln, Nye.

Arsenic guide

This one is worth checking in Clark County.

Fluoride2 of 28 wells over

2 of 28 wells tested here from 2004 to 2015 were over the EPA limit of 4 mg/L, against about 1 in 15 across Nevada. Half the results were under 0.5 mg/L, and the top 1 in 10 were 2.2 mg/L or more. That's a bigger share than in 8 of the 9 other Nevada counties with 10 or more tested wells, leaving out 1 county whose results are likely overstated.

Clark and its neighbors

San Bernardino, CA8%

Clark7%

Mohave, AZ7%

Inyo, CA4%

Nye0%

Too few tested to show: Lincoln.

These 4 are rare in Clark County.

Manganese1 of 28 wells over

1 of 28 wells tested here from 2004 to 2015 was over the EPA health advisory of 0.3 mg/L, against about 1 in 8 across Nevada. At least half the results were too low for the lab to measure, and the top 1 in 10 were 0.15 mg/L or more. That's a smaller share than in 6 of the 9 other Nevada counties with 10 or more tested wells, leaving out 1 county whose results are likely overstated.

Clark and its neighbors

Mohave, AZ8%

Clark4%

San Bernardino, CA3%

Nye2%

Inyo, CA0%

Too few tested to show: Lincoln.

Manganese guide

Uranium0 of 27 wells over

None of the 27 wells tested here from 2004 to 2015 were over the EPA limit of 30 µg/L, against about 1 in 11 across Nevada. Half the results were under 2.2 µg/L, and the top 1 in 10 were 6.5 µg/L or more. Clark County had none, while 4 of the 8 other Nevada counties with 10 or more tested wells had at least one, leaving out 1 county whose results are likely overstated.

Clark and its neighbors

Inyo, CA17%

Mohave, AZ12%

San Bernardino, CA10%

Clark0%

Nye0%

Too few tested to show: Lincoln.

Uranium guide

Nitrate0 of 35 wells over

None of the 35 wells tested here from 2003 to 2015 were over the EPA limit of 10 mg/L, against about 1 in 16 across Nevada. Half the results were under 0.51 mg/L, and the top 1 in 10 were 3.5 mg/L or more. Clark County had none, while 8 of the 11 other Nevada counties with 10 or more tested wells had at least one.

Clark and its neighbors

Mohave, AZ17%

San Bernardino, CA9%

Nye6%

Clark0%

Inyo, CA0%

Lincoln0%

Nitrate guide

Lead0 of 28 wells over

None of the 28 wells tested here from 2004 to 2015 were over the EPA action level of 15 µg/L, against under 1 in 100 across Nevada. At least half the results were too low for the lab to measure, and the top 1 in 10 were 0.51 µg/L or more. Clark County had none, while 1 of the 6 other Nevada counties with 10 or more tested wells had at least one.

Clark and its neighbors

Mohave, AZ2%

Clark0%

Inyo, CA0%

Nye0%

San Bernardino, CA0%

Too few tested to show: Lincoln.

Lead guide

Too few Clark County wells were tested for this one.

Radon in water5 wells tested

Only 5 wells here were tested from 2013 to 2015, too few to say how common it is. Across Nevada it's none.

Radon guide

Coliform bacteria turned up in 1 of 6 tested Clark County wells, so test for it every year.

Coliform bacteria1 of 6 wells had it

1 of 6 wells tested here from 2013 to 2015 had coliform bacteria, against about 1 in 12 across Nevada.

Bacteria guide

E. coli1 of 6 wells had it

1 of 6 wells tested here from 2013 to 2015 had E. coli, against under 1 in 50 across Nevada.

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

Bacteria guide

Iron reached staining levels in 5 of 28 tested wells, and it isn't a health risk.

Iron stains5 of 28 wells had it

About 2 in 10 wells tested here from 2004 to 2015 had enough iron to stain (0.3 mg/L), against about 1 in 9 across Nevada.

Clark and its neighbors

Clark18%

Mohave, AZ14%

Inyo, CA8%

San Bernardino, CA6%

Nye0%

Too few tested to show: Lincoln.

Iron guide

Clark County has 40 tested wells, and the busiest decade for testing was the 2000s.

25 wells had a test in the 2000s and 21 in the 2010s.

None of the 40 wells has a test from 2020 or later, so a fresh test of your own well tells you more than any of these.

Most Clark 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 4 things to check in Clark County.

Bacteria
Nitrate
Arsenic
Fluoride

What Nevada offers well owners

Free testingWe didn't find a free program for all of Nevada. Nevada's private well page
Certified labsNevada's list of certified labs
Well recordsNevada's well record search

Half the household wells here are shallower than 225 feet.

That comes from 10,349 household wells in Nevada's drilling records. Most wells of every kind here are 40 to 300 feet deep. Wells as deep as Clark County's are usually better protected from fertilizer and bacteria at the surface, but they can pick up more of what's in the rock, like arsenic and uranium. Typical household wells here go deeper than in 15 of the 16 other Nevada counties with enough drilling records.

Look up your own well's depth in Nevada's well record search, or see how to find it.

Well depths: US Groundwater Well Database

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

Clark 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 30 town water systems in Clark County test for PFAS. 4 found some PFAS, all below the new limits. No well in Clark 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 Clark County

San Bernardino, CA Nye

Elsewhere in Nevada

Washoe Douglas Lyon

All of Nevada

Questions people ask about well water in Clark County

Is well water in Clark County safe to drink?

8 of 29 wells tested in Clark County had arsenic over the limit, about 3 in 10. Across Nevada it's about 6 in 10. That's a bigger share than in 3 of the 6 other Nevada counties with 10 or more tested wells, leaving out 2 counties whose results are likely overstated. So test your own well for arsenic before you count on it.

Where can I get my well tested in Clark County?

Use a lab Nevada has certified for drinking water. Nevada's list is linked above, in the box about testing. Ask for bacteria, nitrate, arsenic and fluoride, the tests that matter most in Clark County.

How deep are wells in Clark County?

Half the household wells here are shallower than 225 feet. Typical household wells here go deeper than in 15 of the 16 other Nevada counties with enough drilling records.

How does Clark County compare with the counties around it?

For arsenic, the share of tested wells over the limit: Clark County, at 28%, had a higher share than all 3 neighboring counties with data. Groundwater doesn't stop at county lines, so San Bernardino, CA's 24% is worth knowing about if you live near it.

How often should I test my well in Clark County?

In Clark County, 1 of 6 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 Division of Environmental ProtectionUpdated November 8, 2026

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Where the Clark County numbers come from

People on wells: 28,919 in Clark County, from EPA estimates built on the 2020 Census (Murray et al.).
Lab tests: 241 well water samples from 40 wells in the Water Quality Portal, run by the USGS and EPA, 2003 to 2019.
Well depths: 10,349 Nevada drilling records for Clark County, gathered in the US Groundwater Well Database (Lin and others, 2024).
Neighboring counties: the 5 counties that share a border with Clark County, from the Census Bureau's county adjacency file.
PFAS: EPA tests of 30 town water systems in Clark County under the Fifth Unregulated Contaminant Monitoring Rule, 2023 to 2025.
Radon: Clark County is zone 3 on the EPA Map of Radon Zones.
State programs and links: Division of Environmental Protection, checked November 1, 2026.

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