EPA data as of Oct 2026 · page updated 2026-10-30
Montana: drinking water & radon
Montana has 816 active community water systems. Since 2016, 167 reported health-based violations; 4 had a latest lead result above 15 ppb; 2 measured PFOA or PFOS at or above 4 ppt.
Water systems816
With violations167
Radon zone 1 ZIPs359
ZIPs likely on wells308
Radon zones in Montana
tap a countyZone 1 · highestZone 2 · moderateZone 3 · low
Most health-based violations
| Town of Denton 255 people | 77 |
| Fort Belknap Agency Water System 2,600 people | 70 |
| Town of Whitehall 1,500 people | 57 |
| City of Harlem 820 people | 44 |
| St Labre Indian School 650 people | 39 |
| Beaverhead Jackson Water and Sewer Dist 58 people | 27 |
| Town of Philipsburg 1,360 people | 25 |
| King Ranch Colony 56 people | 24 |
| Crow Agency Water System 2,057 people | 17 |
| Riverview Colony 130 people | 16 |
Highest latest lead (90th percentile)
| Hinsdale Water Department 250 people | 29 ppb |
| Town of Dutton 338 people | 27 ppb |
| Fallon County Water District 85 people | 24 ppb |
| Brady County Water Sewer District 144 people | 23 ppb |
| Forest Park Water Users Association 323 people | 15 ppb |
| Cinnabar the 175 people | 15 ppb |
| Absarokee Water and Sewer Dist 1,100 people | 14 ppb |
| Lion Mountain Homeowners Assoc 204 people | 14 ppb |
| City of Great Falls 60,000 people | 12 ppb |
| Yellowtail Dam Gc System 125 people | 11 ppb |
Highest PFOA / PFOS
| Kalispell Public Works 25,000 people | 6.6 ppt |
| Alpine Village Wua 125 people | 4.1 ppt |
Largest systems
| City of Billings 114,000 people | 114,000 |
| Missoula Water 68,200 people | 68,200 |
| City of Great Falls 60,000 people | 60,000 |
| City of Bozeman 56,000 people | 56,000 |
| Butte Silverbow Water Dept 33,000 people | 33,000 |
| Helena Water System 32,091 people | 32,091 |
| Kalispell Public Works 25,000 people | 25,000 |
| Billings Heights Co Water Dist of 12,000 people | 12,000 |
| City of Belgrade 10,460 people | 10,460 |
| City of Whitefish 10,418 people | 10,418 |
All ZIP codes in Montana
399 ZIP codes.
59001Absarokee59002Acton59003Ashland59004Ashland59006Ballantine59007Bearcreek59008Belfry59010Bighorn59011Big Timber59012Birney59013Boyd59014Bridger59015Broadview59016Busby59018Clyde Park59019Columbus59020Cooke City59022Crow Agency59024Custer59025Decker59026Edgar59027Emigrant59028Fishtail59029Fromberg59030Gardiner59031Garryowen59032Grass Range59033Greycliff59034Hardin59035Fort Smith59036Harlowton59037Huntley59038Hysham59039Ingomar59041Joliet59043Lame Deer59044Laurel59046Lavina59047Livingston59050Lodge Grass59052Mc Leod59053Martinsdale59054Melstone59055Melville59057Molt59058Mosby59059Musselshell59061Nye59062Otter59063Park City59064Pompeys Pillar59065Pray59066Pryor59067Rapelje59068Red Lodge59069Reed Point59070Roberts59071Roscoe59072Roundup59073Roundup59074Ryegate59075Saint Xavier59076Sanders59077Sand Springs59078Shawmut59079Shepherd59081Silver Gate59082Springdale59083Sumatra59084Teigen59085Two Dot59086Wilsall59087Winnett59088Worden59089Wyola59101Billings59102Billings59103Billings59104Billings59105Billings59106Billings59107Billings59108Billings59111Billings59112Billings59114Billings59115Billings59116Billings59117Billings59201Wolf Point59211Antelope59212Bainville59213Brockton59214Brockway59215Circle59217Crane59218Culbertson59219Dagmar59221Fairview59222Flaxville59223Fort Peck59225Frazer59226Froid59230Glasgow59231Saint Marie59240Glentana59241Hinsdale59242Homestead59243Lambert59244Larslan59247Medicine Lake59248Nashua59250Opheim59252Outlook59253Peerless59254Plentywood59255Poplar59256Raymond59257Redstone59258Reserve59259Richey59260Richland59261Saco59262Savage59263Scobey59270Sidney59273Vandalia59274Vida59275Westby59276Whitetail59301Miles City59311Alzada59312Angela59313Baker59314Biddle59315Bloomfield59316Boyes59317Broadus59318Brusett59319Capitol59322Cohagen59323Colstrip59324Ekalaka59326Fallon59327Forsyth59330Glendive59332Hammond59333Hathaway59336Ismay59337Jordan59338Kinsey59339Lindsay59343Olive59344Plevna59345Powderville59347Rosebud59349Terry59351Volborg59353Wibaux59354Willard59401Great Falls59403Great Falls59404Great Falls59405Great Falls59406Great Falls59410Augusta59411Babb59412Belt59414Black Eagle59416Brady59417Browning59418Buffalo59419Bynum59420Carter59421Cascade59422Choteau59424Coffee Creek59425Conrad59427Cut Bank59430Denton59432Dupuyer59433Dutton59434East Glacier Park59435Ethridge59436Fairfield59440Floweree59441Forest Grove59442Fort Benton59443Fort Shaw59444Galata59446Geraldine59447Geyser59448Heart Butte59450Highwood59451Hilger59452Hobson59453Judith Gap59454Kevin59456Ledger59457Lewistown59460Loma59461Lothair59462Moccasin59463Monarch59464Moore59465Neihart59466Oilmont59467Pendroy59468Power59469Raynesford59471Roy59472Sand Coulee59474Shelby59477Simms59479Stanford59480Stockett59482Sunburst59483Sun River59484Sweet Grass59485Ulm59486Valier59487Vaughn59489Winifred59501Havre59520Big Sandy59521Box Elder59522Chester59523Chinook59524Dodson59525Gildford59526Harlem59527Hays59528Hingham59529Hogeland59530Inverness59531Joplin59532Kremlin59535Lloyd59537Loring59538Malta59540Rudyard59542Turner59544Whitewater59545Whitlash59546Zortman59547Zurich59601Helena59602Helena59604Helena59620Helena59623Helena59624Helena59626Helena59631Basin59632Boulder59633Canyon Creek59634Clancy59635East Helena59636Fort Harrison59638Jefferson City59639Lincoln59640Marysville59642Ringling59643Toston59644Townsend59645White Sulphur Springs59647Winston59648Wolf Creek59701Butte59702Butte59703Butte59707Butte59710Alder59711Anaconda59713Avon59714Belgrade59715Bozeman59716Big Sky59718Bozeman59719Bozeman59720Cameron59721Cardwell59722Deer Lodge59724Dell59725Dillon59727Divide59728Elliston59729Ennis59730Gallatin Gateway59731Garrison59732Glen59733Gold Creek59735Harrison59736Jackson59739Lima59740Mc Allister59741Manhattan59743Melrose59745Norris59746Polaris59747Pony59748Ramsay59749Sheridan59750Butte59751Silver Star59752Three Forks59754Twin Bridges59755Virginia City59756Warm Springs59758West Yellowstone59759Whitehall59760Willow Creek59761Wisdom59762Wise River59771Bozeman59772Bozeman59801Missoula59802Missoula59803Missoula59804Missoula59806Missoula59807Missoula59808Missoula59812Missoula59820Alberton59821Arlee59823Bonner59824Charlo59825Clinton59826Condon59827Conner59828Corvallis59829Darby59830De Borgia59831Dixon59832Drummond59833Florence59834Frenchtown59835Grantsdale59837Hall59840Hamilton59841Pinesdale59842Haugan59843Helmville59844Heron59845Hot Springs59846Huson59847Lolo59848Lonepine59851Milltown59853Noxon59854Ovando59855Pablo59856Paradise59858Philipsburg59859Plains59860Polson59863Ravalli59864Ronan59865Saint Ignatius59866Saint Regis59867Saltese59868Seeley Lake59870Stevensville59871Sula59872Superior59873Thompson Falls59874Trout Creek59875Victor59901Kalispell59903Kalispell59904Kalispell59910Big Arm59911Bigfork59912Columbia Falls59913Coram59914Dayton59915Elmo59916Essex59917Eureka59918Fortine59919Hungry Horse59920Kila59921Lake Mc Donald59922Lakeside59923Libby59925Marion59926Martin City59927Olney59928Polebridge59929Proctor59930Rexford59931Rollins59932Somers59933Stryker59934Trego59935Troy59936West Glacier59937Whitefish
What this is — and isn’t. These are records your water utility and state reported to the EPA, and the EPA’s radon map for your county. They describe the system and the area, not the water from your own tap or the air in your home. For that, read your utility’s annual Consumer Confidence Report and test: lead and radon tests are inexpensive.
Questions
How many water systems in Montana have violations?
167 of 816 active community water systems in Montana reported at least one health-based violation since 2016 (EPA SDWIS).
What is the radon risk in Montana?
359 ZIP codes are in EPA radon zone 1 (highest potential), 40 in zone 2 and 0 in zone 3. EPA recommends testing every home.