Marion County, AR well water: arsenic, nitrate and what to test for
About 8,900 people in Marion County use a private well (USGS 2010 estimate). Private wells aren’t covered by the Safe Drinking Water Act, so only a lab test shows what’s in yours.
“Test your well water at least once every year for total coliform bacteria, nitrates, total dissolved solids, and pH level.”
CDC- Total coliform bacteriaEvery year
- NitrateEvery year
- Total dissolved solidsEvery year
- pHEvery year
- ArsenicAsk your local health department how often
The model puts about 1 in 100 here above the limit. Only a test shows your well.
EPA: Private Drinking Water Wells · EPA: Protect Your Home’s Water · CDC: Guidelines for Testing Well Water
- After flooding or land disturbance near the well
- After the well is repaired or a part is replaced
- When the water’s taste, colour or smell changes
- If someone in the home is pregnant or nursing
- When an infant or child joins the household
- 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.
Mid-table for both models
Use a state-certified lab
Arkansas Department of Health certifies the laboratories that test drinking water in Arkansas.
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.
Marion County well water
Sources: CDC Well Water Index (2024) · USGS arsenic and nitrate models · USGS domestic well populations · EPA and CDC testing guidance · EPA state certification programs. Data last updated 2026-10-08. All sources →
Do private wells in Marion County have arsenic?
A USGS model estimates that about 1 in 100 of the 8,900 people on private wells in Marion County live where wells are likely to be above the 10 µg/L arsenic limit (about 120 people). That is an estimate for the area, not a result for any well. Only a lab test of your own well shows what is in your water.
What should I test my well for in Marion County?
EPA and CDC say to test every year for total coliform bacteria, nitrate, total dissolved solids and pH. Ask your local health department about arsenic; in Marion County the USGS model puts about 1 in 100 well users above the arsenic limit. The USGS nitrate model's typical level at well depth here is 0.1 mg/L.
How often should I test my well water?
Test your well water at least once every year for total coliform bacteria, nitrates, total dissolved solids, and pH level. (CDC) Test again after flooding, a well repair, or a change in taste, colour or smell, and when someone in the home is pregnant or an infant joins the household.
Where can I get my well tested in Arkansas?
Arkansas Department of Health keeps the list of laboratories certified to test drinking water in Arkansas. Only use laboratories that are certified to do drinking water testing. (EPA)