About 10% of the county's 83,848 residents. Rank 17 of 64 in Louisiana.
95% range 37 to 82 private-well users (2010 base year). Rank 22 of 64 in Louisiana.
Low potential (average indoor radon may be less than 2 pCi/L). EPA says the map should not be used to decide whether an individual home needs testing.
Labs with an address in this county, from the official state lists on this site, matched by ZIP code.
What to test for in St. Landry Parish
Private wells are not regulated like public water: EPA advises owners to test their well every year for total coliform bacteria, nitrates, total dissolved solids and pH. Your state's own schedule:
- The Louisiana Department of Health (LDH) strongly recommends testing for total coliform and E. coli bacteria at least once a year. source
- LDH's well-testing brochure also recommends yearly preliminary tests for chemical contaminants: nitrate/nitrite and metals such as arsenic, lead and cadmium. source
Arsenic. USGS estimates that about 55 people using private wells in St. Landry Parish had arsenic above 10 µg/L, EPA's limit for public water (2010 base year; 95% range 37 to 82). USGS describes this kind of estimate as useful "for broad screening of the population at risk", so it says nothing certain about any one well. Arsenic has no taste or smell: test for it by name.
Radon. EPA puts St. Landry Parish in Zone 3: low potential (average indoor radon may be less than 2 pCi/L). That map is about radon in indoor air, and EPA says it should not be used to decide whether an individual home needs testing. If radon is found in your air and you have a well, EPA suggests testing the water too: see radon in well water.
For anything specific to your home (farms nearby, old plumbing, a new baby, a smell or stain), use the which-tests checklist. When the results arrive, check your numbers against EPA's limits.
Show the numbers
| Item | Value | Note |
|---|---|---|
| St. Tammany Parish | 1,127 people (2010 base year) | |
| Ascension Parish | 610 people (2010 base year) | |
| Tangipahoa Parish | 545 people (2010 base year) | |
| Vermilion Parish | 427 people (2010 base year) | |
| Livingston Parish | 410 people (2010 base year) | |
| St. Landry Parish (this county) | 55 people (2010 base year) |
USGS model estimate for broad screening, not a measurement of any well. Only a test tells you about your own well. Source: USGS, Estimated county level domestic well population with arsenic greater than 10 micrograms per liter (Ayotte, Medalie and Qi, 2017), accessed 2026-11-01.
PFAS in public water near St. Landry Parish (public supply, not your well)
This is public water data, not your well. A private well draws its own groundwater, which can have more or less PFAS than the public supply nearby. Only a test of your well tells you.
Under EPA’s fifth Unregulated Contaminant Monitoring Rule (UCMR 5), public water systems sampled their water for 29 PFAS between Jan 3, 2023 and Jun 17, 2026. 15 public systems that serve ZIP codes mainly in St. Landry Parish reported results. 0 of them had at least one sample with PFOA or PFOS at or above 4.0 ng/L, and 0 had at least one of the 29 PFAS measured at or above its reporting level.
4.0 ng/L (parts per trillion) is both EPA’s UCMR 5 reporting level for PFOA and PFOS and the number in EPA’s 2024 limit for public water. That limit is judged on a running annual average, so one sample at that level is not a violation. EPA proposed changes to its PFAS rules in May 2026: see PFAS in well water for the current status and who should test a well. To test your own well, find a lab certified for PFAS.
Method: a system counts for this county when it reports serving a ZIP code whose largest land part is in this county, so a system serving several counties counts in each. Source: U.S. EPA, UCMR 5 occurrence data (by state), file dated Oct 15, 2026; downloaded Nov 1, 2026.
Testing programs and help in Louisiana
- You can pick up a bacteria sampling kit at an LDH lab or parish health unit, or order one online for home delivery and return it yourself. A sanitarian can also come to your home and collect the sample, for a higher fee. source
- Communities Unlimited field staff, in a program funded by the US EPA, do in-person well assessments in Louisiana: a visual inspection, a check of well construction against state standards and, when possible, a look at the water source. source
Buying a home with a well in St. Landry Parish
Loan test (FHA, VA, USDA) in St. Landry Parish, LA
- VA. Test results are valid for 90 days from the date the local health authority certifies them, unless the local authority says otherwise. VA’s chapter names no list of contaminants: the water must meet the local health authority’s requirements, or EPA guidelines where it has none. Your lender may ask for specific tests.
- FHA. A well test is required in the situations FHA’s handbook lists, among others, and the report may not be more than 180 days old at disbursement.
- USDA. Guaranteed loans need a water quality test for a private well, done by the local health authority or a state-certified lab, and no more than 180 days old at closing.
Lenders can ask for more (extra tests, a particular lab, who takes the sample): ask your lender before you book. Federal rules as read on Nov 3, 2026 source 1 source 2 source 3. Full comparison: VA, FHA and USDA well water test requirements. Loan test kits sold by mail, with price and days to results: kits compared.
State-certified labs in St. Landry Parish
None of the labs on our Louisiana list has an address in St. Landry Parish. Labs elsewhere in the state may take samples by mail or courier: ask the lab, and check the hold time for bacteria before you send one.
Testing by mail from St. Landry Parish. Louisiana Department of Health, bacteriological sampling instructions publishes these prices: Bacteria kit (total coliform / E. coli), self-collected $40 (checked 2 Nov 2026) source. All Louisiana state-lab prices and how to get a kit.
See all Louisiana labs in the finder and filter by the test you need and by labs that take homeowner samples.
- USGS, Estimated use of water in the United States, county-level data for 2015 (Dieter et al., ver. 2.0, 2018)
- USGS, Estimated county level domestic well population with arsenic greater than 10 micrograms per liter (Ayotte, Medalie and Qi, 2017)
- U.S. EPA, Map of Radon Zones, county list (EPA 402/A-16/001)
- U.S. Census Bureau, 2020 ZCTA to county relationship file (lab ZIP codes to counties)
- LDH - 2026 List of Laboratories Certified by Louisiana for Drinking Water Analyses - Chemistry (Current as of 2/12/2026)
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