Tap & Air

Private wells

Indiana well water: who's on a well and what to test for

An estimated 1,478,400 people in 609,800 homes, about 20.9% of Indiana homes, above the national 14.6%. Estimates are from EPA's Water Source 2020 model.

People on private wells

1,478,400

Homes on wells

20.9%

Est. above arsenic limit

150,900

Adams County: about 41% of homes on private wellsAllen County: about 10% of homes on private wellsBartholomew County: about 21% of homes on private wellsBenton County: about 32% of homes on private wellsBlackford County: about 33% of homes on private wellsBoone County: about 18% of homes on private wellsBrown County: about 56% of homes on private wellsCarroll County: about 65% of homes on private wellsCass County: about 42% of homes on private wellsClark County: about 9% of homes on private wellsClay County: about 38% of homes on private wellsClinton County: about 36% of homes on private wellsCrawford County: about 55% of homes on private wellsDaviess County: about 36% of homes on private wellsDearborn County: about 30% of homes on private wellsDecatur County: about 38% of homes on private wellsDeKalb County: about 35% of homes on private wellsDelaware County: about 26% of homes on private wellsDubois County: about 27% of homes on private wellsElkhart County: about 29% of homes on private wellsFayette County: about 29% of homes on private wellsFloyd County: about 6% of homes on private wellsFountain County: about 46% of homes on private wellsFranklin County: about 61% of homes on private wellsFulton County: about 51% of homes on private wellsGibson County: about 27% of homes on private wellsGrant County: about 29% of homes on private wellsGreene County: about 39% of homes on private wellsHamilton County: about 6% of homes on private wellsHancock County: about 25% of homes on private wellsHarrison County: about 52% of homes on private wellsHendricks County: about 13% of homes on private wellsHenry County: about 38% of homes on private wellsHoward County: about 24% of homes on private wellsHuntington County: about 33% of homes on private wellsJackson County: about 31% of homes on private wellsJasper County: about 56% of homes on private wellsJay County: about 43% of homes on private wellsJefferson County: about 25% of homes on private wellsJennings County: about 40% of homes on private wellsJohnson County: about 10% of homes on private wellsKnox County: about 21% of homes on private wellsKosciusko County: about 50% of homes on private wellsLaGrange County: about 79% of homes on private wellsLake County: about 6% of homes on private wellsLaPorte County: about 35% of homes on private wellsLawrence County: about 32% of homes on private wellsMadison County: about 26% of homes on private wellsMarion County: about 0% of homes on private wellsMarshall County: about 49% of homes on private wellsMartin County: about 51% of homes on private wellsMiami County: about 45% of homes on private wellsMonroe County: about 9% of homes on private wellsMontgomery County: about 40% of homes on private wellsMorgan County: about 42% of homes on private wellsNewton County: about 56% of homes on private wellsNoble County: about 49% of homes on private wellsOhio County: about 47% of homes on private wellsOrange County: about 63% of homes on private wellsOwen County: about 72% of homes on private wellsParke County: about 59% of homes on private wellsPerry County: about 35% of homes on private wellsPike County: about 39% of homes on private wellsPorter County: about 23% of homes on private wellsPosey County: about 53% of homes on private wellsPulaski County: about 65% of homes on private wellsPutnam County: about 46% of homes on private wellsRandolph County: about 44% of homes on private wellsRipley County: about 47% of homes on private wellsRush County: about 49% of homes on private wellsSt. Joseph County: about 18% of homes on private wellsScott County: about 31% of homes on private wellsShelby County: about 41% of homes on private wellsSpencer County: about 46% of homes on private wellsStarke County: about 71% of homes on private wellsSteuben County: about 55% of homes on private wellsSullivan County: about 35% of homes on private wellsSwitzerland County: about 59% of homes on private wellsTippecanoe County: about 15% of homes on private wellsTipton County: about 48% of homes on private wellsUnion County: about 54% of homes on private wellsVanderburgh County: about 1% of homes on private wellsVermillion County: about 26% of homes on private wellsVigo County: about 24% of homes on private wellsWabash County: about 39% of homes on private wellsWarren County: about 65% of homes on private wellsWarrick County: about 14% of homes on private wellsWashington County: about 53% of homes on private wellsWayne County: about 25% of homes on private wellsWells County: about 43% of homes on private wellsWhite County: about 49% of homes on private wellsWhitley County: about 55% of homes on private wells
Homes on private wellsUnder 5%5-15%15-30%30-50%50% or more

Every Indiana 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.

Elkhart County66,70029%15.1%1.485 ft
St. Joseph County53,00018%17.9%1.2n/a
Allen County45,40010%9.8%0.0n/a
Kosciusko County41,70050%25.2%0.592 ft
Porter County41,20023%19.8%0.4n/a
LaPorte County40,00035%18.4%1.4n/a
Madison County36,20026%31.1%0.0n/a
LaGrange County33,40079%14.3%1.658 ft
Delaware County31,20026%19.7%0.0n/a
Morgan County31,20042%4.1%0.3n/a
Tippecanoe County30,30015%14.4%0.3n/a
Lake County29,5006%13.0%0.163 ft
Vigo County25,70024%11.3%1.0n/a
Marshall County23,90049%37.0%0.7n/a
Noble County23,40049%16.7%0.3n/a
Howard County22,40024%36.2%0.0n/a
Hendricks County22,10013%9.3%0.1n/a
Harrison County20,40052%1.4%1.3n/a
Hancock County20,40025%43.9%0.0n/a
Hamilton County19,9006%27.4%0.0n/a
Grant County19,60029%5.0%0.0n/a
Whitley County19,40055%14.8%0.0n/a
Bartholomew County19,20021%6.9%0.5n/a
Jasper County19,20056%6.8%0.1n/a
Shelby County19,10041%26.7%0.1n/a
Henry County19,00038%34.6%0.1n/a
Wayne County18,70025%20.6%0.3n/a
Adams County18,70041%10.8%0.0n/a
Steuben County18,20055%20.9%0.3n/a
Starke County16,60071%19.5%0.3n/a
Johnson County16,40010%14.4%0.2n/a
Putnam County16,30046%5.6%0.4n/a
Montgomery County15,90040%24.2%0.180 ft
Cass County15,90042%25.2%0.2n/a
DeKalb County15,90035%13.7%0.0n/a
Owen County15,70072%2.1%0.3n/a
Dearborn County15,60030%2.5%0.8n/a
Washington County15,50053%1.6%1.6n/a
Miami County15,50045%38.0%0.1n/a
Lawrence County14,80032%1.6%1.1n/a
Franklin County14,60061%3.0%1.0n/a
Ripley County14,50047%7.1%0.6n/a
Posey County14,30053%10.6%0.4n/a
Jackson County14,30031%6.0%1.0n/a
Daviess County14,20036%12.3%0.4n/a
Carroll County13,40065%28.4%0.2n/a
Wells County13,10043%12.7%0.0n/a
Boone County13,00018%51.5%0.0n/a
Orange County13,00063%1.4%1.0n/a
Huntington County12,80033%13.7%0.0n/a
Wabash County12,80039%29.6%0.1n/a
Greene County12,50039%4.8%0.3n/a
Monroe County12,4009%1.3%0.9n/a
Dubois County12,00027%8.4%0.7n/a
Clinton County11,80036%50.6%0.0n/a
White County11,70049%19.6%0.1n/a
Clark County11,4009%4.6%1.0n/a
Jennings County11,40040%5.4%0.1n/a
Randolph County11,40044%52.9%0.0n/a
Fulton County10,90051%21.9%0.3n/a
Decatur County10,70038%11.2%0.2n/a
Clay County10,40038%9.0%0.2150 ft
Jay County10,00043%11.2%0.0n/a
Gibson County9,70027%17.8%0.7n/a
Warrick County9,50014%9.6%0.4n/a
Brown County9,40056%1.6%0.1n/a
Spencer County9,20046%2.3%0.5n/a
Parke County9,00059%13.3%0.3n/a
Rush County8,60049%23.5%0.1n/a
Jefferson County8,50025%4.8%0.5n/a
Knox County8,30021%5.0%0.9n/a
Pulaski County8,20065%23.2%0.0n/a
Perry County7,90035%2.6%0.2n/a
Scott County7,80031%4.7%0.4n/a
Newton County7,80056%5.5%0.1n/a
Tipton County7,70048%30.9%0.0n/a
Fountain County7,50046%15.0%0.2110 ft
Fayette County7,30029%10.4%2.8n/a
Sullivan County7,10035%8.0%0.4n/a
Crawford County6,50055%1.5%0.2n/a
Switzerland County6,00059%5.4%0.6n/a
Warren County5,60065%17.3%0.0n/a
Floyd County5,4006%1.5%0.6n/a
Pike County5,10039%5.9%0.3n/a
Martin County5,00051%2.9%0.3n/a
Blackford County4,20033%6.0%0.0n/a
Vermillion County4,10026%19.6%0.4n/a
Union County3,90054%5.1%1.4n/a
Benton County3,00032%12.4%0.0n/a
Ohio County3,00047%4.9%0.7n/a
Vanderburgh County2,5001%11.2%0.4n/a
Marion County4800%9.7%0.1n/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

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-range
See today's price on Amazon

2. 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

Budget
See today's price on Amazon

3. 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

Premium
See today's price on Amazon

4. 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

Premium
See today's price on Amazon

5. 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

$539.00
Buy at Waterdrop

Price at Waterdrop, checked Oct 5, 2026or compare on Amazon

iSpring RCC7AK reverse osmosis

Mid-range
See today's price on Amazon

6. 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-range
See today's price on Amazon
Get free well water treatment quotes

Questions

Which Indiana counties rely most on wells?+

By share of homes: LaGrange County (79%), Owen County (72%), Starke County (71%), Pulaski County (65%), Warren County (65%). By number of people: Elkhart County (66,700), St. Joseph County (53,000), Allen County (45,400).

Is arsenic a problem in Indiana wells?+

USGS estimates about 150,900 Indiana well users have water above the 10 microgram per liter arsenic limit that applies to public systems, the largest numbers in Kosciusko County, Allen County, Madison 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 Indiana?+

We could not confirm a statewide rule for Indiana. 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).