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

Related Rankings

Home Safety 2026 Water compliance, PFAS, radon, and annual AQI score inputs PFAS 2026 Forever chemicals detected in drinking water Lead Risk 2026 Lead service-line indicators and system-level action-level exceedances
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.

Get safety alerts for Wisconsin

Free updates when EPA data changes for this area. No spam.

Unsubscribe anytime. Privacy Policy.

Share This Page

X Facebook
Check your water filter options Free tool - no phone call required.