About 5% of the county's 71,735 residents. Rank 2 of 5 in Hawaii.
The USGS county table has no value for this county.
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 Kauai County
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:
- Hawaii's Department of Health says there are no regulations controlling water quality in private wells serving individual homes and no requirements for regular testing. It refers owners to EPA's advice: test each year for total coliform bacteria, nitrates and any other contaminants of concern in your area, more often if you suspect a problem. EPA also suggests considering pesticides, organic chemicals and heavy metals before first use. source
Radon. EPA puts Kauai County 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.
PFAS in public water near Kauai County (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. 7 public systems that serve ZIP codes mainly in Kauai County 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 Hawaii
- For rainwater catchment used in the home, DOH recommends a screening test for E. coli, turbidity, lead and copper by a lab certified or approved by DOH, with the sample taken after all treatment, such as at the kitchen tap. source
- Rainwater catchment homes: the DOH Safe Drinking Water Branch subsidizes a lead and copper test once a year for the owner or user of a legal dwelling served by a rainwater catchment system. The owner pays shipping and $25 for the analysis; DOH is billed the rest. AECOS Laboratory, Inc. is currently the only participating lab. This program covers catchment systems, not wells. source
Buying a home with a well in Kauai County
Loan test (FHA, VA, USDA) in Kauai County, HI
- 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 Kauai County
None of the labs on our Hawaii list has an address in Kauai County. 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.
See all Hawaii 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)
- Hawaii DOH State Laboratories Division - Certified Chemistry & Radiochemistry Drinking Water Labs (August 12th, 2026)
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