Least Reliable Water Systems in Iowa — 2026

Out of 1,058 ZIP codes with data in Iowa, these are the lowest-ranked areas for reliability score. See also: National Least Reliable Water Systems in America | All Iowa Rankings

Statistic	Value
ZIP codes ranked	1,058
Lowest value	10/100
Median value	75/100
State	Iowa

100 Lowest-Ranked ZIP Codes

Rank	ZIP Code	City	State	Reliability Score	Safety Score
1	51540	Hastings	IA	10/100	47/100
2	50112	Grinnell	IA	15/100	36/100
3	50557	Lehigh	IA	23/100	44/100
4	52310	Monticello	IA	27/100	64/100
5	50464	Plymouth	IA	30/100	61/100
6	51451	Lanesboro	IA	30/100	50/100
7	50611	Bristow	IA	31/100	55/100
8	52341	Toddville	IA	32/100	66/100
9	50853	Massena	IA	34/100	60/100
10	52322	Oxford	IA	34/100	55/100
11	52338	Swisher	IA	34/100	65/100
12	50158	Marshalltown	IA	35/100	47/100
13	50501	Fort Dodge	IA	35/100	35/100
14	50562	Mallard	IA	35/100	46/100
15	51440	Dedham	IA	35/100	50/100
16	52251	Ladora	IA	35/100	42/100
17	50247	State Center	IA	40/100	59/100
18	50622	Denver	IA	40/100	59/100
19	51555	Missouri Valley	IA	40/100	46/100
20	51650	Riverton	IA	40/100	62/100
21	52208	Belle Plaine	IA	40/100	44/100
22	52212	Center Junction	IA	40/100	62/100
23	52240	Iowa City	IA	40/100	46/100
24	52242	Iowa City	IA	40/100	51/100
25	52243	Iowa City	IA	40/100	50/100
26	52244	Iowa City	IA	40/100	50/100
27	52245	Iowa City	IA	40/100	51/100
28	52246	Iowa City	IA	40/100	46/100
29	52301	Marengo	IA	40/100	50/100
30	52649	Salem	IA	40/100	62/100
31	52755	Lone Tree	IA	40/100	64/100
32	50009	Altoona	IA	42/100	65/100
33	50128	Jamaica	IA	42/100	32/100
34	50005	Albion	IA	45/100	64/100
35	50066	Dawson	IA	45/100	45/100
36	50109	Granger	IA	45/100	66/100
37	50138	Knoxville	IA	45/100	59/100
38	50423	Britt	IA	45/100	62/100
39	50431	Coulter	IA	45/100	64/100
40	50439	Goodell	IA	45/100	64/100
41	50449	Klemme	IA	45/100	64/100
42	50451	Lakota	IA	45/100	64/100
43	50591	Thor	IA	45/100	54/100
44	51020	Galva	IA	45/100	64/100
45	51535	Griswold	IA	45/100	61/100
46	51558	Moorhead	IA	45/100	58/100
47	51652	Sidney	IA	45/100	59/100
48	52203	Amana	IA	45/100	66/100
49	52204	Amana	IA	45/100	62/100
50	52241	Coralville	IA	45/100	52/100
51	52255	Lowden	IA	45/100	66/100
52	52317	North Liberty	IA	45/100	66/100
53	52340	Tiffin	IA	45/100	66/100
54	52359	West Chester	IA	45/100	64/100
55	52536	Blakesburg	IA	45/100	64/100
56	52542	Cantril	IA	45/100	64/100
57	52550	Delta	IA	45/100	64/100
58	52574	Mystic	IA	45/100	60/100
59	52726	Blue Grass	IA	45/100	68/100
60	52759	Montpelier	IA	45/100	53/100
61	50213	Osceola	IA	46/100	56/100
62	50453	Leland	IA	47/100	69/100
63	50140	Lamoni	IA	49/100	65/100
64	50002	Adair	IA	50/100	56/100
65	50123	Humeston	IA	50/100	61/100
66	50130	Jewell	IA	50/100	48/100
67	50167	Minburn	IA	50/100	64/100
68	50261	Van Meter	IA	50/100	68/100
69	50274	Wiota	IA	50/100	59/100
70	50434	Fertile	IA	50/100	64/100
71	50436	Forest City	IA	50/100	68/100
72	50469	Rockwell	IA	50/100	64/100
73	50480	Titonka	IA	50/100	66/100
74	50484	Woden	IA	50/100	61/100
75	50530	Dayton	IA	50/100	60/100
76	50552	Knierim	IA	50/100	60/100
77	50648	Jesup	IA	50/100	63/100
78	50845	Diagonal	IA	50/100	59/100
79	51058	Sutherland	IA	50/100	64/100
80	51241	Larchwood	IA	50/100	64/100
81	51247	Rock Valley	IA	50/100	63/100
82	51545	Little Sioux	IA	50/100	65/100
83	51551	Malvern	IA	50/100	63/100
84	52001	Dubuque	IA	50/100	59/100
85	52002	Dubuque	IA	50/100	64/100
86	52003	Dubuque	IA	50/100	59/100
87	52004	Dubuque	IA	50/100	64/100
88	52099	Dubuque	IA	50/100	60/100
89	52215	Chelsea	IA	50/100	54/100
90	52247	Kalona	IA	50/100	68/100
91	52254	Lost Nation	IA	50/100	61/100
92	52333	Solon	IA	50/100	63/100
93	52358	West Branch	IA	50/100	58/100
94	52591	Sigourney	IA	50/100	64/100
95	52722	Bettendorf	IA	50/100	43/100
96	52777	Wheatland	IA	50/100	68/100
97	50541	Gilmore City	IA	52/100	65/100
98	52205	Anamosa	IA	52/100	61/100
99	52761	Muscatine	IA	52/100	54/100
100	50008	Allerton	IA	53/100	64/100

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.