2026 Rankings

Least Reliable Water Systems in Wisconsin — 2026

Last updated: June 4, 2026

902 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 902 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 902
Lowest value 15/100
Median value 65/100
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 54901 Oshkosh WI 24/100 55/100
12 54902 Oshkosh WI 24/100 50/100
13 54903 Oshkosh WI 24/100 60/100
14 54904 Oshkosh WI 24/100 55/100
15 54906 Oshkosh WI 24/100 53/100
16 53118 Dousman WI 25/100 63/100
17 53168 Salem WI 25/100 63/100
18 53186 Waukesha WI 25/100 41/100
19 53187 Waukesha WI 25/100 36/100
20 53188 Waukesha WI 25/100 41/100
21 53189 Waukesha WI 25/100 46/100
22 53955 Poynette WI 25/100 61/100
23 54880 Superior WI 25/100 61/100
24 54986 Winneconne WI 25/100 64/100
25 53050 Mayville WI 26/100 53/100
26 54632 Genoa WI 26/100 54/100
27 54766 Sheldon WI 26/100 79/100
28 53073 Plymouth WI 27/100 76/100
29 53150 Muskego WI 27/100 64/100
30 53191 Williams Bay WI 27/100 61/100
31 54128 Gresham WI 27/100 69/100
32 53170 Silver Lake WI 29/100 70/100
33 53199 Silver Lake WI 29/100 73/100
34 53932 Fall River WI 29/100 77/100
35 54409 Antigo WI 30/100 56/100
36 54848 Ladysmith WI 30/100 69/100
37 53924 Cazenovia WI 32/100 69/100
38 53581 Richland Center WI 33/100 46/100
39 53569 Montfort WI 34/100 64/100
40 54555 Phillips WI 34/100 77/100
41 54729 Chippewa Falls WI 34/100 70/100
42 54774 Chippewa Falls WI 34/100 73/100
43 53140 Kenosha WI 35/100 69/100
44 53141 Kenosha WI 35/100 69/100
45 53142 Kenosha WI 35/100 69/100
46 53143 Kenosha WI 35/100 69/100
47 53144 Kenosha WI 35/100 64/100
48 54481 Stevens Point WI 35/100 46/100
49 54482 Stevens Point WI 35/100 42/100
50 54492 Stevens Point WI 35/100 42/100
51 54741 Fairchild WI 35/100 76/100
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 53585 Sharon WI 37/100 65/100
59 53925 Columbus WI 37/100 61/100
60 54001 Amery WI 37/100 79/100
61 54455 Mosinee WI 37/100 66/100
62 54750 Maiden Rock WI 37/100 66/100
63 54773 Whitehall WI 37/100 79/100
64 54822 Cameron WI 37/100 82/100
65 54868 Rice Lake WI 37/100 82/100
66 54645 Mount Sterling WI 38/100 28/100
67 54806 Ashland WI 38/100 45/100
68 53091 Theresa WI 39/100 65/100
69 53185 Waterford WI 39/100 73/100
70 53534 Edgerton WI 39/100 43/100
71 53577 Plain WI 39/100 77/100
72 53582 Ridgeway WI 39/100 56/100
73 54526 Glen Flora WI 39/100 81/100
74 54652 Readstown WI 39/100 60/100
75 53115 Delavan WI 40/100 52/100
76 53128 Genoa City WI 40/100 56/100
77 53555 Lodi WI 40/100 43/100
78 54524 Fifield WI 40/100 79/100
79 53536 Evansville WI 41/100 61/100
80 53578 Prairie Du Sac WI 41/100 79/100
81 53965 Wisconsin Dells WI 41/100 77/100
82 54541 Laona WI 41/100 76/100
83 53038 Johnson Creek WI 42/100 69/100
84 53080 Saukville WI 42/100 68/100
85 53125 Fontana WI 42/100 69/100
86 53149 Mukwonago WI 42/100 69/100
87 53167 Rochester WI 42/100 81/100
88 53588 Spring Green WI 42/100 64/100
89 53960 Rio WI 42/100 79/100
90 54017 New Richmond WI 42/100 61/100
91 54021 Prescott WI 42/100 61/100
92 54436 Granton WI 42/100 78/100
93 54733 Dallas WI 42/100 82/100
94 53811 Hazel Green WI 43/100 66/100
95 53181 Twin Lakes WI 44/100 81/100
96 53183 Wales WI 44/100 68/100
97 53228 Milwaukee WI 44/100 80/100
98 53541 Gratiot WI 44/100 65/100
99 53825 Stitzer WI 44/100 60/100
100 54215 Kellnersville WI 44/100 48/100

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.

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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