Private wells
South Dakota well water: who's on a well and what to test for
People on private wells
220,200
Homes on wells
25.0%
Est. above arsenic limit
1,200
Every South Dakota county
Sorted by people on private wells. Arsenic and nitrate are modeled for typical wells in the county, not measured at yours; depth is the median of domestic well records.
| Pennington County | 15,200 | 15% | 2.9% | 0.8 | 125 ft |
| Minnehaha County | 12,500 | 6% | 5.0% | 1.1 | 113 ft |
| Davison County | 11,200 | 56% | 2.5% | 0.7 | 140 ft |
| Lawrence County | 7,900 | 33% | 2.5% | 0.4 | 180 ft |
| Meade County | 7,800 | 27% | 2.8% | 0.7 | 140 ft |
| Brown County | 7,400 | 19% | 9.8% | 0.1 | 52 ft |
| Oglala Lakota | 7,400 | 56% | n/a | n/a | 140 ft |
| Lincoln County | 6,000 | 9% | 6.6% | 0.7 | 155 ft |
| Brookings County | 5,700 | 16% | 4.0% | 0.8 | 54 ft |
| Turner County | 5,400 | 62% | 4.9% | 0.6 | 143 ft |
| Todd County | 5,200 | 54% | 3.2% | 2.0 | 151 ft |
| Custer County | 5,200 | 63% | 3.4% | 0.8 | 140 ft |
| Roberts County | 4,800 | 49% | 6.3% | 0.3 | 82 ft |
| Union County | 4,400 | 26% | 4.6% | 1.2 | 111 ft |
| Charles Mix County | 4,300 | 41% | 2.5% | 0.1 | 280 ft |
| Dewey County | 4,300 | 79% | 3.2% | 0.3 | 90 ft |
| Codington County | 4,000 | 12% | 5.1% | 0.7 | 65 ft |
| Beadle County | 3,900 | 22% | 3.1% | 0.0 | 91 ft |
| Hutchinson County | 3,600 | 49% | 4.4% | 0.2 | 201 ft |
| Yankton County | 3,500 | 15% | 4.4% | 0.2 | 160 ft |
| Day County | 3,400 | 61% | 3.2% | 0.2 | 140 ft |
| Hamlin County | 3,300 | 49% | 5.0% | 0.7 | 60 ft |
| Lake County | 3,200 | 27% | 3.6% | 0.3 | 186 ft |
| Grant County | 3,100 | 37% | 6.8% | 0.4 | 83 ft |
| Corson County | 3,000 | 74% | 4.5% | 0.3 | 165 ft |
| Butte County | 2,900 | 26% | 3.0% | 0.3 | 180 ft |
| Moody County | 2,800 | 40% | 4.9% | 1.4 | 40 ft |
| Hanson County | 2,700 | 84% | 2.9% | 0.4 | 160 ft |
| Hand County | 2,600 | 85% | 5.0% | 0.3 | 110 ft |
| Marshall County | 2,600 | 66% | 7.9% | 0.1 | 105 ft |
| Spink County | 2,500 | 40% | 6.3% | 0.0 | 70 ft |
| Edmunds County | 2,500 | 58% | 5.2% | 0.1 | 158 ft |
| Perkins County | 2,500 | 84% | 4.3% | 0.2 | 200 ft |
| Aurora County | 2,400 | 86% | 3.5% | 0.1 | 262 ft |
| Hughes County | 2,400 | 12% | 3.4% | 0.2 | 60 ft |
| McCook County | 2,400 | 39% | 3.8% | 0.1 | 192 ft |
| Fall River County | 2,300 | 32% | 4.5% | 0.7 | 200 ft |
| Deuel County | 2,200 | 45% | 6.0% | 0.6 | 99 ft |
| Potter County | 2,200 | 83% | 3.6% | 0.3 | 46 ft |
| Clay County | 2,200 | 16% | 4.3% | 0.6 | 103 ft |
| Clark County | 2,100 | 48% | 3.0% | 0.1 | 125 ft |
| Tripp County | 2,100 | 39% | 2.4% | 1.9 | 75 ft |
| Brule County | 2,000 | 37% | 3.0% | 0.1 | n/a |
| Bon Homme County | 2,000 | 32% | 3.1% | 0.1 | 236 ft |
| Lyman County | 1,900 | 60% | 2.7% | 0.0 | n/a |
| Kingsbury County | 1,900 | 35% | 4.4% | 0.1 | 135 ft |
| Gregory County | 1,900 | 46% | 2.4% | 2.3 | 60 ft |
| Douglas County | 1,900 | 61% | 3.0% | 0.1 | 380 ft |
| Bennett County | 1,900 | 56% | 3.9% | 1.3 | 122 ft |
| Ziebach County | 1,700 | 75% | 3.8% | 0.3 | 160 ft |
| Haakon County | 1,700 | 89% | 3.2% | 0.3 | 43 ft |
| Jackson County | 1,700 | 60% | 3.3% | 1.1 | 100 ft |
| Sanborn County | 1,600 | 68% | 2.9% | 0.1 | 160 ft |
| Mellette County | 1,600 | 84% | 3.0% | 1.2 | 57 ft |
| Sully County | 1,300 | 83% | 3.6% | 0.4 | 55 ft |
| Miner County | 1,200 | 53% | 2.9% | 0.0 | 170 ft |
| Campbell County | 1,200 | 82% | 5.0% | 0.5 | 60 ft |
| Hyde County | 1,200 | 94% | 4.2% | 0.5 | 132 ft |
| Walworth County | 1,100 | 20% | 4.0% | 0.5 | 71 ft |
| Harding County | 1,000 | 75% | 5.3% | 0.3 | 185 ft |
| Faulk County | 930 | 49% | 5.4% | 0.0 | 132 ft |
| Buffalo County | 890 | 49% | 3.7% | 0.1 | 95 ft |
| McPherson County | 790 | 33% | 6.5% | 0.2 | 120 ft |
| Stanley County | 740 | 24% | 2.7% | 0.0 | 50 ft |
| Jerauld County | 710 | 39% | 3.6% | 0.5 | 131 ft |
| Jones County | 390 | 41% | 2.6% | 0.1 | n/a |
Shading: red is among the highest counties nationally, amber the middle, green the lower range. Click a column to sort.
Most well users above the arsenic limit
- Pennington County: about 340 people
- Meade County: about 230 people
- Custer County: about 110 people
- Lincoln County: about 80 people
- Perkins County: about 70 people
Test first, then treat what the test finds
We may earn a commission from links below, at no cost to you. Picks follow the testing order, not who pays. How we make money.
1. Certified lab well test
Start here, every year
A mail-in kit analyzed by a certified lab measures bacteria, nitrate, arsenic, metals and more. Test strips cannot measure arsenic or uranium reliably.
Mail-in certified lab well water test
Mid-range2. Sediment pre-filter
Sand, silt or cloudy water
A 5-micron cartridge after the pressure tank catches sand, silt and rust before they reach fixtures or other filters. Cartridges are cheap and swap every few months.
5-micron whole-house sediment filter
Budget3. Iron and sulfur filter
Orange stains or rotten-egg smell
Air-injection or oxidizing-media filters remove orange staining and rotten-egg smell. Size one from a lab result for iron, manganese and hydrogen sulfide.
Air-injection iron and sulfur filter
Premium4. UV disinfection system
Coliform bacteria in a test
Inactivates bacteria and viruses; usually for private wells or after boil notices.
12 GPM whole-house UV purifier
Premium5. Under-sink reverse osmosis
Arsenic, nitrate or uranium in a test
The most thorough option for drinking water: PFAS, lead, nitrate, arsenic and more. Look for NSF/ANSI 58.
Waterdrop G3P600 tankless RO
Price at Waterdrop, checked Oct 5, 2026or compare on Amazon
iSpring RCC7AK reverse osmosis
Mid-range6. Whole-house well filter
Several problems at once
Multi-stage sediment and carbon for every tap. Add UV if bacteria shows up, and choose stages from your lab results, not a guess.
Waterdrop WHF21 2-stage whole-house filter
Mid-rangeQuestions
Which South Dakota counties rely most on wells?+
By share of homes: Hyde County (94%), Haakon County (89%), Aurora County (86%), Hand County (85%), Hanson County (84%). By number of people: Pennington County (15,200), Minnehaha County (12,500), Davison County (11,200).
Is arsenic a problem in South Dakota wells?+
USGS estimates about 1,200 South Dakota well users have water above the 10 microgram per liter arsenic limit that applies to public systems, the largest numbers in Pennington County, Meade County, Custer County. Arsenic has no taste or smell, so only a lab test finds it.
Do I have to test my well when I sell a house in South Dakota?+
We could not confirm a statewide rule for South Dakota. Check with your county health department. Buyers can still make a lab test a condition of the offer.
How often should I test my well?+
No federal law covers private wells. EPA's drinking water limits apply to public water systems, so testing and treating a private well is up to the owner. EPA and CDC recommend testing at least once a year for coliform bacteria, nitrate, pH and total dissolved solids, and testing for arsenic, uranium, radon and other local concerns based on where you live.
Well-user counts, arsenic and nitrate figures are each a modeled estimate built from national datasets, not a count of tested wells, and well depths summarize drilling records rather than every well. Your own well can be very different from the county average, which is why the only answer for your home is a lab test. Sources: EPA Office of Research and Development, Water Source 2020 (private well estimates by census block); CDC Environmental Public Health Tracking, Well Water Index (from USGS nitrate and arsenic models); USGS, county-level domestic well population with arsenic above 10 micrograms per liter (Ayotte and others, 2017); USGS Synthesized Domestic Well Database for the Conterminous United States (SynDWell-US), McCarthy and others, 2025 (depth, where a county has 30+ usable records).