Water Quality Report · Updated May 12, 2026
MODESTO, CITY OF
MODESTO, CITY OF delivers tap water graded F (47/100) by TapWaterSafety.org. The utility serves approximately 218,771 residents in MODESTO, California using surface water (purchased). The most significant water quality concerns are: PFAS contamination; Perfluorohexane sulfonate (PFHXS) significantly above health guideline; Arsenic significantly above health guideline; Haloacetic acids (HAA5) significantly above health guideline. For questions, the utility can be reached at 209-342-4592.
Is MODESTO tap water safe to drink?
MODESTO, CITY OF delivers tap water that earns a grade of F (47/100) from TapWaterSafety.org — a poor rating, with significant contamination concerns and/or recent violations.
The utility serves 218,771 residents in MODESTO, drawing from surface water (purchased).
Public testing data identifies 20 contaminants in this water above EWG's health-based guidelines, including: Perfluorohexane sulfonate (PFHXS), Arsenic, Haloacetic acids (HAA5), Haloacetic acids (HAA9), Total trihalomethanes (TTHMs), Trichloroacetic acid, Chromium (hexavalent), Chloroform, Dichloroacetic acid, Bromodichloromethane, Nitrate, Uranium, Dibromochloromethane, Dibromoacetic acid, Perfluorooctanoic acid (PFOA), Tetrachloroethylene (perchloroethylene), Perfluorooctane sulfonate (PFOS), Bromate*, 1,2,3-Trichloropropane, 1,2-Dibromo-3-chloropropane (DBCP). For most residents, a properly certified home filter at the kitchen tap is the most cost-effective way to reduce exposure to whatever's in your water. See our filter recommendations below, matched specifically to this utility's contaminant profile.
Quick actions for MODESTO residents
Top concerns in this water
Based on the most recent EPA and EWG data, these are the most significant water quality issues for MODESTO, CITY OF.
PFAS contamination
Severe concernPerfluorooctane sulfonate (PFOS), Perfluorooctanoic acid (PFOA) detected. PFAS are persistent chemicals linked to cancer and immune effects with no known safe exposure threshold.
Perfluorohexane sulfonate (PFHXS) significantly above health guideline
Moderate concernPerfluorohexane sulfonate (PFHXS) detected at 0.493 ppt, 493x above the EWG health guideline of 0.001 ppt.
Arsenic significantly above health guideline
Moderate concernArsenic detected at 1.73 ppb, 434x above the EWG health guideline of 0.004 ppb.
Haloacetic acids (HAA5) significantly above health guideline
Moderate concernHaloacetic acids (HAA5) detected at 36.2 ppb, 362x above the EWG health guideline of 0.1 ppb.
Contact MODESTO, CITY OF
Reach the utility directly for service issues, water quality concerns, or to request your Consumer Confidence Report.
General Contact
Treatment Plant
Recommended water filters for MODESTO
Filters matched to the specific contaminants in this water supply.
Reverse Osmosis or NSF P473 certified carbon
$80-$750Activated carbon and RO are the only technologies proven to remove PFAS at certified levels.
Reverse Osmosis
$249-$750Arsenic is most effectively removed by reverse osmosis. Some specialized adsorptive filters also work.
Carbon block (NSF/ANSI 42 + 53)
$40-$750Activated carbon is highly effective for disinfection byproducts like TTHM and HAA5.
Disclosure: TapWaterSafety earns a commission from purchases made through these links. This does not influence our scoring methodology or filter selection.
Score breakdown
This utility's overall score of 47/100 breaks down across five weighted components. Read the full methodology →
Contaminants detected — international standards comparison
Every contaminant detected, compared side-by-side against US EPA legal limits, the EU Drinking Water Directive (2020/2184), WHO Guidelines, and California's Public Health Goal (the strictest US benchmark). Why we show multiple standards →
| Contaminant | Detected | EWG US health-based |
EPA US legal |
EU DWD Europe |
WHO global |
CA PHG strictest US |
Tested sample year |
Status |
|---|---|---|---|---|---|---|---|---|
| Perfluorohexane sulfonate (PFHXS) PFAS |
0.493 ppt | 0.001 | 10.0 | — | — | — | — | 493× over |
| Arsenic Heavy metal |
1.73 ppb | 0.004 | 10.0 | 10 | 10 | 0.004 | — | 434× over |
| Haloacetic acids (HAA5) Disinfection byproduct |
36.2 ppb | 0.1 | 60.0 | 60 | — | — | — | 362× over |
| Haloacetic acids (HAA9) Disinfection byproduct |
20.1 ppb | 0.06 | — | — | — | — | — | 335× over |
| Total trihalomethanes (TTHMs) Disinfection byproduct |
44.8 ppb | 0.15 | 80.0 | 100 | — | — | — | 299× over |
| Trichloroacetic acid Disinfection byproduct |
13.5 ppb | 0.1 | — | — | — | — | — | 135× over |
| Chromium (hexavalent) Heavy metal |
2.58 ppb | 0.02 | — | — | — | — | — | 129× over |
| Chloroform Disinfection byproduct |
41.0 ppb | 0.4 | — | — | — | — | — | 103× over |
| Dichloroacetic acid Disinfection byproduct |
14.3 ppb | 0.2 | — | — | — | — | — | 72× over |
| Bromodichloromethane Disinfection byproduct |
2.33 ppb | 0.06 | — | — | — | — | — | 39× over |
| Nitrate Inorganic |
5.12 ppm | 0.14 | 10.0 | 11.3 | 11.3 | 10 | — | 37× over |
| Uranium Radiological |
6.32 pCi/L | 0.43 | 20.0 | 30 | 30 | 0.43 | — | 15× over |
| Dibromochloromethane Disinfection byproduct |
1.05 ppb | 0.1 | — | — | — | — | — | 10× over |
| Dibromoacetic acid Disinfection byproduct |
0.148 ppb | 0.03 | — | — | — | — | — | 4.9× over |
| Perfluorooctanoic acid (PFOA) PFAS |
0.397 ppt | 0.09 | 4.0 | 100 | 100 | 0.007 | — | 4.4× over |
| Tetrachloroethylene (perchloroethylene) Volatile organic compound |
0.228 ppb | 0.06 | 5.0 | — | — | — | — | 3.8× over |
| Perfluorooctane sulfonate (PFOS) PFAS |
0.966 ppt | 0.3 | 4.0 | 100 | 100 | 1 | — | 3.2× over |
| Bromate* Disinfection byproduct |
0.268 ppb | 0.1 | 10.0 | 10 | 10 | 0.1 | — | 2.7× over |
| 1,2,3-Trichloropropane Other |
0.000935 ppb | 0.0007 | — | — | — | — | — | 1.3× over |
| 1,2-Dibromo-3-chloropropane (DBCP) Other |
0.00183 ppb | 0.0017 | 0.2 | — | — | — | — | 1.1× over |
| Vanadium Other |
16.9 ppb | 21.0 | — | — | — | — | — | Below guideline |
| Bromoform Disinfection byproduct |
0.371 ppb | 0.5 | — | — | — | — | — | Below guideline |
| Chlorate Disinfection byproduct |
146.3 ppb | 210.0 | — | — | — | — | — | Below guideline |
| Trichloroethylene Volatile organic compound |
0.0489 ppb | 0.4 | 5.0 | 10 | 20 | 1.7 | — | Below guideline |
| Barium Heavy metal |
71.5 ppb | 700.0 | 2000.0 | — | 1300 | 2000 | — | Below guideline |
| Molybdenum Other |
1.25 ppb | 40.0 | — | — | — | — | — | Below guideline |
| 1,4-Dioxane Semi-volatile organic compound |
0.00755 ppb | 0.35 | — | — | 50 | 1 | — | Below guideline |
| Manganese Heavy metal |
0.885 ppb | 100.0 | — | 50 | 80 | — | — | Below guideline |
| Monochloroacetic acid Disinfection byproduct |
0.0989 ppb | 53.0 | — | — | — | — | — | Below guideline |
| Aluminum Heavy metal |
0.943 ppb | 600.0 | — | 200 | — | 600 | — | Below guideline |
| Strontium Radiological |
0.584 ppb | 1500.0 | — | — | — | — | — | Below guideline |
| Perfluoropentanoic Acid (PFPeA) PFAS |
0.321 ppt | 1000.0 | — | — | — | — | — | Below guideline |
| Perfluorohexanoic Acid (PFHxA) PFAS |
0.193 ppt | 1000.0 | — | — | — | — | — | Below guideline |
| 1,1-Dichloroethane Volatile organic compound |
0.00025 ppb | 3.0 | — | — | — | — | — | Below guideline |
| Perfluorobutane sulfonate (PFBS) PFAS |
0.157 ppt | 2000.0 | — | — | — | — | — | Below guideline |
| Perfluorobutanoic Acid (PFBA) PFAS |
0.052 ppt | 1000.0 | — | — | — | — | — | Below guideline |
| Perfluoroheptanoic acid (PFHPA) PFAS |
0.02 ppt | 1000.0 | — | — | — | — | — | Below guideline |
| Xylenes (total) Volatile organic compound |
0.00349 ppb | 1800.0 | 10000.0 | — | — | — | — | Below guideline |
| Bromide* Other |
144.9 ppb | — | — | — | — | — | — | Below guideline |
| Chlorodifluoromethane Other |
0.124 ppb | — | — | — | — | — | — | Below guideline |
| Dichlorodifluoromethane Other |
0.112 ppb | — | — | — | — | — | — | Below guideline |
| Fluoride Inorganic |
0.0258 ppm | — | 4.0 | 1.5 | 1.5 | — | — | Below guideline |
| Lithium Other |
2.03 ppb | — | — | — | — | — | — | Below guideline |
All values in the unit of the detected level. Red cells indicate the detected level exceeds that standard. Some contaminants have limits in some jurisdictions but not others (shown as —). The "Tested" column shows the year each contaminant sample was collected.
Sources: US EPA, EU Drinking Water Directive 2020/2184, WHO Guidelines (4th ed.), California OEHHA PHGs, EWG Tap Water Database.
MODESTO, CITY OF service area
This water system serves 1 community in Stanislaus County, California. Click any city for its dedicated tap water quality page.
Find the right filter for MODESTO water
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