Out of 2,674 ZIP codes with data in California, these are the lowest-ranked areas for reliability score. See also: National Least Reliable Water Systems in America | All California Rankings
| Statistic | Value |
|---|---|
| ZIP codes ranked | 2,674 |
| Lowest value | 10/100 |
| Median value | 75/100 |
| State | California |
100 Lowest-Ranked ZIP Codes
| Rank | ZIP Code | City | State | Reliability Score | Safety Score |
|---|---|---|---|---|---|
| 1 | 91903 | Alpine | CA | 10/100 | 69/100 |
| 2 | 91931 | Guatay | CA | 10/100 | 33/100 |
| 3 | 91963 | Potrero | CA | 10/100 | 55/100 |
| 4 | 91990 | Potrero | CA | 10/100 | 55/100 |
| 5 | 92365 | Newberry Springs | CA | 10/100 | 50/100 |
| 6 | 93285 | Wofford Heights | CA | 10/100 | 58/100 |
| 7 | 93643 | North Fork | CA | 10/100 | 50/100 |
| 8 | 93644 | Oakhurst | CA | 10/100 | 57/100 |
| 9 | 93669 | Wishon | CA | 10/100 | 35/100 |
| 10 | 94570 | Moraga | CA | 10/100 | 45/100 |
| 11 | 92266 | Palo Verde | CA | 13/100 | 80/100 |
| 12 | 92327 | Daggett | CA | 15/100 | 17/100 |
| 13 | 92338 | Ludlow | CA | 15/100 | 50/100 |
| 14 | 93243 | Lebec | CA | 15/100 | 58/100 |
| 15 | 93247 | Lindsay | CA | 15/100 | 28/100 |
| 16 | 93283 | Weldon | CA | 15/100 | 55/100 |
| 17 | 93534 | Lancaster | CA | 15/100 | 48/100 |
| 18 | 93535 | Lancaster | CA | 15/100 | 43/100 |
| 19 | 93536 | Lancaster | CA | 15/100 | 43/100 |
| 20 | 93539 | Lancaster | CA | 15/100 | 36/100 |
| 21 | 93584 | Lancaster | CA | 15/100 | 36/100 |
| 22 | 93586 | Lancaster | CA | 15/100 | 36/100 |
| 23 | 94130 | San Francisco | CA | 15/100 | 53/100 |
| 24 | 94515 | Calistoga | CA | 15/100 | 70/100 |
| 25 | 95461 | Middletown | CA | 15/100 | 65/100 |
| 26 | 96122 | Portola | CA | 15/100 | 59/100 |
| 27 | 95563 | Salyer | CA | 16/100 | 83/100 |
| 28 | 91416 | Encino | CA | 18/100 | 17/100 |
| 29 | 91426 | Encino | CA | 18/100 | 17/100 |
| 30 | 93287 | Woody | CA | 18/100 | 32/100 |
| 31 | 93635 | Los Banos | CA | 18/100 | 82/100 |
| 32 | 92384 | Shoshone | CA | 19/100 | 77/100 |
| 33 | 95942 | Forest Ranch | CA | 19/100 | 87/100 |
| 34 | 92069 | San Marcos | CA | 20/100 | 66/100 |
| 35 | 92078 | San Marcos | CA | 20/100 | 71/100 |
| 36 | 92079 | San Marcos | CA | 20/100 | 69/100 |
| 37 | 92096 | San Marcos | CA | 20/100 | 69/100 |
| 38 | 95201 | Stockton | CA | 20/100 | 77/100 |
| 39 | 95205 | Stockton | CA | 20/100 | 77/100 |
| 40 | 95206 | Stockton | CA | 20/100 | 72/100 |
| 41 | 95207 | Stockton | CA | 20/100 | 72/100 |
| 42 | 95208 | Stockton | CA | 20/100 | 77/100 |
| 43 | 95209 | Stockton | CA | 20/100 | 77/100 |
| 44 | 95210 | Stockton | CA | 20/100 | 77/100 |
| 45 | 95212 | Stockton | CA | 20/100 | 72/100 |
| 46 | 95213 | Stockton | CA | 20/100 | 77/100 |
| 47 | 95214 | Stockton | CA | 20/100 | 77/100 |
| 48 | 95219 | Stockton | CA | 20/100 | 72/100 |
| 49 | 95231 | French Camp | CA | 20/100 | 62/100 |
| 50 | 95267 | Stockton | CA | 20/100 | 77/100 |
| 51 | 95269 | Stockton | CA | 20/100 | 77/100 |
| 52 | 95296 | Stockton | CA | 20/100 | 77/100 |
| 53 | 95297 | Stockton | CA | 20/100 | 77/100 |
| 54 | 95559 | Phillipsville | CA | 22/100 | 91/100 |
| 55 | 93239 | Kettleman City | CA | 23/100 | 51/100 |
| 56 | 93245 | Lemoore | CA | 23/100 | 70/100 |
| 57 | 93501 | Mojave | CA | 23/100 | 58/100 |
| 58 | 93502 | Mojave | CA | 23/100 | 50/100 |
| 59 | 93620 | Dos Palos | CA | 23/100 | 55/100 |
| 60 | 94972 | Valley Ford | CA | 23/100 | 60/100 |
| 61 | 95307 | Ceres | CA | 23/100 | 71/100 |
| 62 | 95333 | Le Grand | CA | 23/100 | 62/100 |
| 63 | 92201 | Indio | CA | 24/100 | 67/100 |
| 64 | 92202 | Indio | CA | 24/100 | 62/100 |
| 65 | 92203 | Indio | CA | 24/100 | 67/100 |
| 66 | 92339 | Forest Falls | CA | 24/100 | 45/100 |
| 67 | 93261 | Richgrove | CA | 24/100 | 62/100 |
| 68 | 93526 | Independence | CA | 24/100 | 73/100 |
| 69 | 93942 | Monterey | CA | 24/100 | 73/100 |
| 70 | 95313 | Crows Landing | CA | 24/100 | 74/100 |
| 71 | 91901 | Alpine | CA | 25/100 | 66/100 |
| 72 | 91962 | Pine Valley | CA | 25/100 | 45/100 |
| 73 | 92311 | Barstow | CA | 25/100 | 45/100 |
| 74 | 92312 | Barstow | CA | 25/100 | 39/100 |
| 75 | 93240 | Lake Isabella | CA | 25/100 | 59/100 |
| 76 | 93267 | Strathmore | CA | 25/100 | 39/100 |
| 77 | 93274 | Tulare | CA | 25/100 | 50/100 |
| 78 | 93275 | Tulare | CA | 25/100 | 39/100 |
| 79 | 93426 | Bradley | CA | 25/100 | 69/100 |
| 80 | 93446 | Paso Robles | CA | 25/100 | 51/100 |
| 81 | 93447 | Paso Robles | CA | 25/100 | 48/100 |
| 82 | 93560 | Rosamond | CA | 25/100 | 28/100 |
| 83 | 93615 | Cutler | CA | 25/100 | 55/100 |
| 84 | 93666 | Sultana | CA | 25/100 | 64/100 |
| 85 | 93926 | Gonzales | CA | 25/100 | 53/100 |
| 86 | 94101 | San Francisco | CA | 25/100 | 53/100 |
| 87 | 94119 | San Francisco | CA | 25/100 | 53/100 |
| 88 | 94120 | San Francisco | CA | 25/100 | 59/100 |
| 89 | 94125 | San Francisco | CA | 25/100 | 53/100 |
| 90 | 94126 | San Francisco | CA | 25/100 | 53/100 |
| 91 | 94128 | San Francisco | CA | 25/100 | 53/100 |
| 92 | 94129 | San Francisco | CA | 25/100 | 53/100 |
| 93 | 94136 | San Francisco | CA | 25/100 | 53/100 |
| 94 | 94137 | San Francisco | CA | 25/100 | 53/100 |
| 95 | 94139 | San Francisco | CA | 25/100 | 53/100 |
| 96 | 94140 | San Francisco | CA | 25/100 | 53/100 |
| 97 | 94141 | San Francisco | CA | 25/100 | 53/100 |
| 98 | 94142 | San Francisco | CA | 25/100 | 53/100 |
| 99 | 94143 | San Francisco | CA | 25/100 | 53/100 |
| 100 | 94144 | San Francisco | CA | 25/100 | 53/100 |
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.
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