Least Reliable Water Systems in Montana — 2026

Out of 408 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	408
Lowest value	10/100
Median value	70/100
State	Montana

100 Lowest-Ranked ZIP Codes

Rank	ZIP Code	City	State	Reliability Score	Safety Score
1	59430	Denton	MT	10/100	45/100
2	59542	Turner	MT	10/100	22/100
3	59526	Harlem	MT	15/100	40/100
4	59759	Whitehall	MT	15/100	45/100
5	59858	Philipsburg	MT	15/100	33/100
6	59038	Hysham	MT	20/100	56/100
7	59648	Wolf Creek	MT	20/100	34/100
8	59086	Wilsall	MT	24/100	62/100
9	59003	Ashland	MT	25/100	33/100
10	59004	Ashland	MT	25/100	33/100
11	59035	Fort Smith	MT	25/100	33/100
12	59457	Lewistown	MT	25/100	40/100
13	59501	Havre	MT	25/100	44/100
14	59523	Chinook	MT	33/100	49/100
15	59270	Sidney	MT	35/100	45/100
16	59601	Helena	MT	35/100	42/100
17	59602	Helena	MT	35/100	37/100
18	59604	Helena	MT	35/100	47/100
19	59620	Helena	MT	35/100	37/100
20	59623	Helena	MT	35/100	37/100
21	59624	Helena	MT	35/100	37/100
22	59625	Helena	MT	35/100	37/100
23	59626	Helena	MT	35/100	37/100
24	59416	Brady	MT	36/100	55/100
25	59524	Dodson	MT	37/100	69/100
26	59634	Clancy	MT	40/100	52/100
27	59425	Conrad	MT	41/100	55/100
28	59472	Sand Coulee	MT	42/100	69/100
29	59029	Fromberg	MT	44/100	68/100
30	59222	Flaxville	MT	45/100	56/100
31	59248	Nashua	MT	45/100	43/100
32	59337	Jordan	MT	45/100	56/100
33	59301	Miles City	MT	46/100	54/100
34	59353	Wibaux	MT	47/100	69/100
35	59433	Dutton	MT	47/100	65/100
36	59450	Highwood	MT	47/100	65/100
37	59484	Sweet Grass	MT	47/100	28/100
38	59755	Virginia City	MT	48/100	61/100
39	59034	Hardin	MT	50/100	56/100
40	59087	Winnett	MT	50/100	71/100
41	59211	Antelope	MT	50/100	60/100
42	59230	Glasgow	MT	50/100	39/100
43	59411	Babb	MT	50/100	61/100
44	59645	White Sulphur Springs	MT	50/100	62/100
45	59756	Warm Springs	MT	50/100	54/100
46	59522	Chester	MT	51/100	64/100
47	59489	Winifred	MT	52/100	65/100
48	59829	Darby	MT	52/100	66/100
49	59323	Colstrip	MT	54/100	65/100
50	59474	Shelby	MT	54/100	64/100
51	59019	Columbus	MT	55/100	59/100
52	59032	Grass Range	MT	55/100	67/100
53	59050	Lodge Grass	MT	55/100	67/100
54	59054	Melstone	MT	55/100	80/100
55	59079	Shepherd	MT	55/100	77/100
56	59243	Lambert	MT	55/100	49/100
57	59410	Augusta	MT	55/100	68/100
58	59419	Bynum	MT	55/100	62/100
59	59442	Fort Benton	MT	55/100	61/100
60	59464	Moore	MT	55/100	63/100
61	59471	Roy	MT	55/100	63/100
62	59714	Belgrade	MT	55/100	56/100
63	59913	Coram	MT	55/100	63/100
64	59446	Geraldine	MT	57/100	65/100
65	59635	East Helena	MT	57/100	69/100
66	59074	Ryegate	MT	59/100	81/100
67	59006	Ballantine	MT	60/100	53/100
68	59025	Decker	MT	60/100	40/100
69	59031	Garryowen	MT	60/100	40/100
70	59046	Lavina	MT	60/100	53/100
71	59058	Mosby	MT	60/100	53/100
72	59064	Pompeys Pillar	MT	60/100	63/100
73	59069	Reed Point	MT	60/100	55/100
74	59077	Sand Springs	MT	60/100	40/100
75	59081	Silver Gate	MT	60/100	53/100
76	59083	Sumatra	MT	60/100	53/100
77	59084	Teigen	MT	60/100	40/100
78	59088	Worden	MT	60/100	55/100
79	59089	Wyola	MT	60/100	40/100
80	59101	Billings	MT	60/100	65/100
81	59102	Billings	MT	60/100	70/100
82	59103	Billings	MT	60/100	73/100
83	59104	Billings	MT	60/100	75/100
84	59105	Billings	MT	60/100	70/100
85	59106	Billings	MT	60/100	70/100
86	59107	Billings	MT	60/100	73/100
87	59108	Billings	MT	60/100	73/100
88	59111	Billings	MT	60/100	73/100
89	59112	Billings	MT	60/100	73/100
90	59114	Billings	MT	60/100	73/100
91	59115	Billings	MT	60/100	73/100
92	59116	Billings	MT	60/100	73/100
93	59117	Billings	MT	60/100	73/100
94	59201	Wolf Point	MT	60/100	53/100
95	59218	Culbertson	MT	60/100	68/100
96	59219	Dagmar	MT	60/100	40/100
97	59225	Frazer	MT	60/100	40/100
98	59257	Redstone	MT	60/100	40/100
99	59258	Reserve	MT	60/100	40/100
100	59274	Vida	MT	60/100	40/100

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: 2026-06-04.

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.