Arsenic is worth checking in Montgomery County wells.
1 worth checking, 6 rare out of 7 health checks.
From 41 wells tested in Montgomery 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
1 in 6 people 106,343 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)
Less likely, but the EPA still says test your air.
Radon zones: EPA map
Here's how Montgomery County compares with Texas and the counties around it.
Each result puts Montgomery County next to the 6 counties that border it, on the chart's 0 to 50% scale.
This one is worth checking in Montgomery County.
Arsenic1 of 20 wells over
Too few tested to show: Grimes, Liberty, San Jacinto, Walker, Waller.
These 6 are rare in Montgomery County.
Nitrate0 of 19 wells over
Too few tested to show: Grimes, Liberty, San Jacinto, Walker, Waller.
Fluoride0 of 40 wells over
Too few tested to show: Grimes, Liberty, San Jacinto, Walker, Waller.
Manganese0 of 35 wells over
Too few tested to show: Grimes, Liberty, San Jacinto, Walker, Waller.
Uranium0 of 20 wells over
Too few tested to show: Grimes, Liberty, San Jacinto, Walker, Waller.
Radon in water0 of 13 wells over
Too few tested to show: Grimes, Liberty, San Jacinto, Walker, Waller.
Lead0 of 20 wells over
Too few tested to show: Grimes, Liberty, San Jacinto, Walker, Waller.
Coliform bacteria turned up in 3 of 6 tested Montgomery County wells, so test for it every year.
Coliform bacteria3 of 6 wells had it
E. coli1 of 6 wells had it
E. coli means human or animal waste is getting in, so if a test of your Montgomery County well finds it, boil drinking water until the well is fixed.
Iron reached staining levels in 3 of 40 tested wells, and it isn't a health risk.
Iron stains3 of 40 wells had it
Too few tested to show: Grimes, Liberty, San Jacinto, Walker, Waller.
Montgomery County has 41 tested wells, and the busiest decade for testing was the 2010s.
None of the 41 wells has a test from 2020 or later, so a fresh test of your own well tells you more than any of these.
Most Montgomery 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 Montgomery County.
- Bacteria
- Nitrate
- Arsenic
What Texas offers well owners
- Free testingTexas A&M AgriLife Extension's Texas Well Owner Network holds periodic county well water screenings, some free and some for a small per-sample fee. See the program
- Certified labsTexas's list of certified labs
- Well recordsTexas's well record search
Half the household wells here are shallower than 221 feet.
That comes from 9,389 household wells in Texas's drilling records. Most wells of every kind here are 190 to 306 feet deep. Wells as deep as Montgomery 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 are shallower than in 146 of the 248 other Texas counties with enough drilling records.
Look up your own well's depth in Texas'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 Montgomery County.
Montgomery 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 44 town water systems in Montgomery County test for PFAS. 1 of them had at least one test above 4 ng/L, the new EPA limit for PFOA and PFOS. The highest single result was 4.8 ng/L of PFOA. No well in Montgomery 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 Montgomery County
Is well water in Montgomery County safe to drink?
1 of 20 wells tested in Montgomery County had arsenic over the limit, about 1 in 20. Across Texas it's about 1 in 10. That's a bigger share than in 12 of the 16 other Texas counties with 10 or more tested wells, leaving out 1 county whose results are likely overstated. So test your own well for arsenic before you count on it.
Can I get my well tested for free in Montgomery County?
Texas A&M AgriLife Extension's Texas Well Owner Network holds periodic county well water screenings, some free and some for a small per-sample fee. If not, use a lab Texas has certified for drinking water. Ask for bacteria, nitrate and arsenic, the tests that matter most in Montgomery County.
How deep are wells in Montgomery County?
Half the household wells here are shallower than 221 feet. Typical household wells here are shallower than in 146 of the 248 other Texas counties with enough drilling records.
How does Montgomery County compare with the counties around it?
For arsenic, the share of tested wells over the limit: Harris, the one neighbor with data, came in lower than Montgomery County, at 2% against 5%. Groundwater doesn't stop at county lines, so Harris's 2% is worth knowing about if you live near it.
How often should I test my well in Montgomery County?
In Montgomery County, 3 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.
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Where the Montgomery County numbers come from
- People on wells: 106,343 in Montgomery County, from EPA estimates built on the 2020 Census (Murray et al.).
- Lab tests: 298 well water samples from 41 wells in the Water Quality Portal, run by the USGS and EPA, 2000 to 2017.
- Well depths: 9,389 Texas drilling records for Montgomery County, gathered in the US Groundwater Well Database (Lin and others, 2024).
- Neighboring counties: the 6 counties that share a border with Montgomery County, from the Census Bureau's county adjacency file.
- PFAS: EPA tests of 44 town water systems in Montgomery County under the Fifth Unregulated Contaminant Monitoring Rule, 2023 to 2025.
- Radon: Montgomery County is zone 3 on the EPA Map of Radon Zones.
- State programs and links: Texas Water Development Board and Texas Commission on Environmental Quality (TCEQ), checked November 1, 2026.