Least Reliable Water Systems in Montana — 2026

Out of 405 ZIP codes with data in Montana, these are the lowest-ranked areas for reliability score. See also: National Least Reliable Water Systems in America | All Montana Rankings

Statistic	Value
ZIP codes ranked	405
Lowest value	10/100
Median value	74/100
State	Montana

100 Lowest-Ranked ZIP Codes

Rank	ZIP Code	City	State	Reliability Score	Safety Score
1	59038	Hysham	MT	10/100	56/100
2	59430	Denton	MT	10/100	45/100
3	59542	Turner	MT	10/100	22/100
4	59457	Lewistown	MT	15/100	40/100
5	59526	Harlem	MT	15/100	40/100
6	59759	Whitehall	MT	15/100	45/100
7	59858	Philipsburg	MT	15/100	33/100
8	59648	Wolf Creek	MT	20/100	34/100
9	59523	Chinook	MT	23/100	49/100
10	59086	Wilsall	MT	24/100	62/100
11	59003	Ashland	MT	25/100	33/100
12	59035	Fort Smith	MT	25/100	33/100
13	59270	Sidney	MT	25/100	45/100
14	59501	Havre	MT	25/100	44/100
15	59601	Helena	MT	25/100	42/100
16	59602	Helena	MT	25/100	37/100
17	59625	Helena	MT	25/100	37/100
18	59301	Miles City	MT	36/100	54/100
19	59416	Brady	MT	36/100	55/100
20	59524	Dodson	MT	37/100	69/100
21	59034	Hardin	MT	40/100	56/100
22	59230	Glasgow	MT	40/100	39/100
23	59634	Clancy	MT	40/100	52/100
24	59425	Conrad	MT	41/100	55/100
25	59522	Chester	MT	41/100	64/100
26	59472	Sand Coulee	MT	42/100	69/100
27	59029	Fromberg	MT	44/100	68/100
28	59222	Flaxville	MT	45/100	56/100
29	59248	Nashua	MT	45/100	43/100
30	59337	Jordan	MT	45/100	56/100
31	59714	Belgrade	MT	45/100	56/100
32	59353	Wibaux	MT	47/100	69/100
33	59433	Dutton	MT	47/100	65/100
34	59446	Geraldine	MT	47/100	65/100
35	59450	Highwood	MT	47/100	65/100
36	59484	Sweet Grass	MT	47/100	28/100
37	59755	Virginia City	MT	48/100	61/100
38	59087	Winnett	MT	50/100	71/100
39	59211	Antelope	MT	50/100	60/100
40	59411	Babb	MT	50/100	61/100
41	59645	White Sulphur Springs	MT	50/100	62/100
42	59756	Warm Springs	MT	50/100	54/100
43	59859	Plains	MT	50/100	68/100
44	59241	Hinsdale	MT	52/100	41/100
45	59489	Winifred	MT	52/100	65/100
46	59829	Darby	MT	52/100	66/100
47	59323	Colstrip	MT	54/100	65/100
48	59474	Shelby	MT	54/100	64/100
49	59032	Grass Range	MT	55/100	67/100
50	59050	Lodge Grass	MT	55/100	67/100
51	59053	Martinsdale	MT	55/100	64/100
52	59054	Melstone	MT	55/100	80/100
53	59079	Shepherd	MT	55/100	77/100
54	59243	Lambert	MT	55/100	49/100
55	59410	Augusta	MT	55/100	68/100
56	59419	Bynum	MT	55/100	62/100
57	59442	Fort Benton	MT	55/100	61/100
58	59456	Ledger	MT	55/100	52/100
59	59464	Moore	MT	55/100	63/100
60	59471	Roy	MT	55/100	63/100
61	59639	Lincoln	MT	55/100	61/100
62	59722	Deer Lodge	MT	55/100	58/100
63	59824	Charlo	MT	55/100	52/100
64	59913	Coram	MT	55/100	63/100
65	59635	East Helena	MT	57/100	69/100
66	59263	Scobey	MT	58/100	51/100
67	59936	West Glacier	MT	58/100	56/100
68	59074	Ryegate	MT	59/100	81/100
69	59482	Sunburst	MT	59/100	64/100
70	59019	Columbus	MT	60/100	59/100
71	59041	Joliet	MT	60/100	61/100
72	59101	Billings	MT	60/100	65/100
73	59102	Billings	MT	60/100	70/100
74	59105	Billings	MT	60/100	70/100
75	59106	Billings	MT	60/100	70/100
76	59218	Culbertson	MT	60/100	68/100
77	59221	Fairview	MT	60/100	68/100
78	59427	Cut Bank	MT	60/100	64/100
79	59758	West Yellowstone	MT	60/100	67/100
80	59853	Noxon	MT	60/100	66/100
81	59874	Trout Creek	MT	60/100	62/100
82	59912	Columbia Falls	MT	60/100	63/100
83	59932	Somers	MT	60/100	63/100

Methodology

Water system reliability scores (0-100) combine violation frequency, violation recency, resolution rate, and system size. Systems with repeated health-based violations and unresolved issues score lowest. The reliability score focuses specifically on the water utility performance, distinct from the broader Home Safety Score.

Data sources: EPA Safe Drinking Water Information System (SDWIS), FEMA National Flood Insurance Program, EPA radon zone maps, EIA electricity rates, and Consumer Confidence Reports. Last updated: 2026-04-13.

Frequently Asked Questions

What does a low water reliability score mean?

A low reliability score (below 50) indicates a water system with frequent violations, poor resolution rates, or recurring compliance issues. These systems may have aging infrastructure, inadequate treatment, or management challenges.

How is reliability different from safety score?

The reliability score focuses specifically on the water utility performance (violations, resolution, compliance). The Home Safety Score is broader, also including lead risk, radon, and flood data. A ZIP code can have a reliable water system but still have high radon or flood risk.