2026 Rankings

Least Reliable Water Systems in Wisconsin — 2026

Last updated: April 13, 2026

898 ZIP codes ranked by Reliability Score #1: ZIP 53072 (Pewaukee, WI) - 15/100
Lead Violations Lowest Score Safest Flood Risk Energy Cost Radon PFAS Reliability EJ Index Homebuyer Risk CO & Gas Safest Gas Remediation Burden Unresolved Violations (by Utility) Water Equity (by Utility)

Out of 898 ZIP codes with data in Wisconsin, these are the lowest-ranked areas for reliability score. See also: National Least Reliable Water Systems in America | All Wisconsin Rankings

Statistic Value
ZIP codes ranked 898
Lowest value 15/100
Median value 67/100
State Wisconsin

100 Lowest-Ranked ZIP Codes

Rank ZIP Code City State Reliability Score Safety Score
1 53072 Pewaukee WI 15/100 40/100
2 53549 Jefferson WI 15/100 40/100
3 53956 Randolph WI 15/100 40/100
4 53957 Randolph WI 15/100 40/100
5 53157 Pell Lake WI 18/100 54/100
6 53522 Browntown WI 19/100 65/100
7 53094 Watertown WI 21/100 28/100
8 53098 Watertown WI 21/100 28/100
9 53130 Hales Corners WI 22/100 74/100
10 53182 Union Grove WI 24/100 81/100
11 53118 Dousman WI 25/100 63/100
12 53168 Salem WI 25/100 63/100
13 53955 Poynette WI 25/100 61/100
14 54481 Stevens Point WI 25/100 46/100
15 54482 Stevens Point WI 25/100 42/100
16 54492 Stevens Point WI 25/100 42/100
17 54986 Winneconne WI 25/100 64/100
18 53050 Mayville WI 26/100 53/100
19 54632 Genoa WI 26/100 54/100
20 54766 Sheldon WI 26/100 79/100
21 53073 Plymouth WI 27/100 76/100
22 53150 Muskego WI 27/100 64/100
23 54128 Gresham WI 27/100 69/100
24 53170 Silver Lake WI 29/100 70/100
25 53199 Silver Lake WI 29/100 73/100
26 53932 Fall River WI 29/100 77/100
27 54409 Antigo WI 30/100 56/100
28 54848 Ladysmith WI 30/100 69/100
29 53924 Cazenovia WI 32/100 69/100
30 53581 Richland Center WI 33/100 46/100
31 53569 Montfort WI 34/100 64/100
32 54555 Phillips WI 34/100 77/100
33 54729 Chippewa Falls WI 34/100 70/100
34 54774 Chippewa Falls WI 34/100 73/100
35 54901 Oshkosh WI 34/100 55/100
36 54902 Oshkosh WI 34/100 50/100
37 54903 Oshkosh WI 34/100 60/100
38 54904 Oshkosh WI 34/100 55/100
39 54906 Oshkosh WI 34/100 53/100
40 53140 Kenosha WI 35/100 69/100
41 53141 Kenosha WI 35/100 69/100
42 53142 Kenosha WI 35/100 69/100
43 53143 Kenosha WI 35/100 69/100
44 53144 Kenosha WI 35/100 64/100
45 53186 Waukesha WI 35/100 41/100
46 53187 Waukesha WI 35/100 36/100
47 53188 Waukesha WI 35/100 41/100
48 53189 Waukesha WI 35/100 46/100
49 53191 Williams Bay WI 35/100 61/100
50 54741 Fairchild WI 35/100 76/100
51 54880 Superior WI 35/100 61/100
52 54121 Florence WI 36/100 77/100
53 54125 Goodman WI 36/100 76/100
54 54514 Butternut WI 36/100 79/100
55 54638 Kendall WI 36/100 72/100
56 53097 Mequon WI 37/100 74/100
57 53105 Burlington WI 37/100 49/100
58 53167 Rochester WI 37/100 81/100
59 53585 Sharon WI 37/100 65/100
60 54001 Amery WI 37/100 79/100
61 54455 Mosinee WI 37/100 66/100
62 54773 Whitehall WI 37/100 79/100
63 54822 Cameron WI 37/100 82/100
64 54868 Rice Lake WI 37/100 82/100
65 54645 Mount Sterling WI 38/100 28/100
66 54806 Ashland WI 38/100 45/100
67 53091 Theresa WI 39/100 65/100
68 53185 Waterford WI 39/100 73/100
69 53534 Edgerton WI 39/100 43/100
70 53577 Plain WI 39/100 77/100
71 53582 Ridgeway WI 39/100 56/100
72 54526 Glen Flora WI 39/100 81/100
73 54652 Readstown WI 39/100 60/100
74 53128 Genoa City WI 40/100 56/100
75 53555 Lodi WI 40/100 43/100
76 54524 Fifield WI 40/100 79/100
77 53536 Evansville WI 41/100 61/100
78 53578 Prairie Du Sac WI 41/100 79/100
79 53965 Wisconsin Dells WI 41/100 77/100
80 54541 Laona WI 41/100 76/100
81 53038 Johnson Creek WI 42/100 69/100
82 53125 Fontana WI 42/100 69/100
83 53149 Mukwonago WI 42/100 69/100
84 53588 Spring Green WI 42/100 64/100
85 53960 Rio WI 42/100 79/100
86 54021 Prescott WI 42/100 61/100
87 54436 Granton WI 42/100 78/100
88 54733 Dallas WI 42/100 82/100
89 53811 Hazel Green WI 43/100 66/100
90 53181 Twin Lakes WI 44/100 81/100
91 53183 Wales WI 44/100 68/100
92 53541 Gratiot WI 44/100 65/100
93 53825 Stitzer WI 44/100 60/100
94 54215 Kellnersville WI 44/100 48/100
95 53172 South Milwaukee WI 45/100 72/100
96 53925 Columbus WI 45/100 61/100
97 54759 Pepin WI 45/100 59/100
98 53018 Delafield WI 46/100 67/100
99 54460 Owen WI 46/100 80/100
100 54625 Dodge WI 46/100 55/100

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.

Explore More Rankings

How this ranking is calculated, data sources, and limitations: Rankings Methodology →

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Disclaimer: Rankings are based on EPA, FEMA, and federal agency data. They reflect historical patterns and risk indicators, not necessarily current conditions. For the most current information, contact your local water utility or request a Consumer Confidence Report.

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