Hardness
Very hard average199mg/L as CaCO₃
System average; range 33–388
USGS hardness classes
About 11.6 grains per gallon. Your current blend may differ from the annual average.
2025View source
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Stanislaus County Water Quality Report
Showing utility report
City of Modesto — Modesto System
2025 utility report; each result retains its measurement period
Results for City of Modesto — Modesto System in Stanislaus County. Confirm the supplier and system on your bill.
Your water at a glance
See the amount, the comparison and what it means. “Below” refers to the stated benchmark, not zero risk.
Chlorine
Reported level below MRDL0.91mg/L
Average; range 0.03–1.6
MRDL: 4 mg/L
Match the filter to the disinfectant used by this utility.
2025View source
TTHMs
Reported level below benchmark25.0µg/L (ppb)
Locational running annual average; range 2–48.5
Report MCL: 80 µg/L
A system result does not measure the water at an individual home.
2025View source
HAA5
Reported level below benchmark13.3µg/L (ppb)
Locational running annual average; range 0–40.1
Report MCL: 60 µg/L
A system result does not measure the water at an individual home.
2025View source
Fluoride
Below report benchmark0.02mg/L
Average; range 0–0.12
California MCL: 2 mg/L
Standard filtration and softening do not establish fluoride reduction.
2025View source
Lead
90th percentile below action levelNDµg/L (ppb)
90th percentile; 52 sampled sites
Report action level: 15 µg/L
No sampled sites exceeded the report’s action level. Household plumbing can change the result at your tap.
2024View source
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Continue with your home details for general filtration guidance. We will not use another utility’s numbers as your result.
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Explore well-water systems →Water hardness by provider
The figures below are provider-specific. They are not a countywide average.
| Utility | Hardness | Hardness source |
|---|---|---|
| 199 mg/L · Very hard average | 2025 |
View Full Water ReportOpen the measured results, dates, comparisons and original utility report.
The numbers behind your report
Selected results with the original sampling dates and measurement basis. Open the utility report for every parameter, notice and footnote.
Open the complete utility report ↗
| What was measured | Reported amount | Sample year / source date | How to read it |
|---|---|---|---|
| Hardness | 199 mg/L as CaCO₃System average; range 33–388 | 2025View source ↗ | Very hard averageAbout 11.6 grains per gallon. Your current blend may differ from the annual average. |
| Chlorine | 0.91 mg/LAverage; range 0.03–1.6 | 2025View source ↗ | Reported level below MRDLMatch the filter to the disinfectant used by this utility. |
| TTHMs | 25.0 µg/L (ppb)Locational running annual average; range 2–48.5 | 2025View source ↗ | Reported level below benchmarkA system result does not measure the water at an individual home. |
| HAA5 | 13.3 µg/L (ppb)Locational running annual average; range 0–40.1 | 2025View source ↗ | Reported level below benchmarkA system result does not measure the water at an individual home. |
| Fluoride | 0.02 mg/LAverage; range 0–0.12 | 2025View source ↗ | Below report benchmarkStandard filtration and softening do not establish fluoride reduction. |
| Lead | ND µg/L (ppb)90th percentile; 52 sampled sites | 2024View source ↗ | 90th percentile below action levelNo sampled sites exceeded the report’s action level. Household plumbing can change the result at your tap. |
| Nitrate as nitrogen | 3.8 mg/LAverage; range 0–8.9 | 2025View source ↗ | Reported average below benchmarkNitrate requires treatment selected for that specific contaminant. |
| Arsenic | 2.2 µg/L (ppb)Average; range 0–9.6 | 2025View source ↗ | Below report benchmarkA whole-home filter needs a specific arsenic reduction claim to address this substance. |
In drinking water, ppm ≈ mg/L, ppb ≈ µg/L and ppt ≈ ng/L. Calculated hardness in grains per US gallon (gpg) = mg/L as CaCO₃ ÷ 17.118, rounded to one decimal. ND means below the reporting limit, not zero.
MCL is an enforceable contaminant limit; MRDL is a disinfectant limit. A PHG is a health goal, not the legal limit. Lead/copper action levels use system sampling percentiles, not a safe-tap threshold. TTHM/HAA5 comparisons use locational running annual averages.
PFAS results are compound-specific. Source monitoring, entry-point samples and tap tests are different. Notification and response levels in a utility report are not maximum contaminant levels; do not infer a compliance violation from a single value. EPA PFAS benchmarks and implementation ↗
Turn your report into a plan for your home.
Choose the system size, keep useful existing equipment, and review your filtration goals.
Source water. Groundwater wells and treated surface water supplied through Modesto Irrigation District at Modesto Reservoir.
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What this means for your home
Modesto’s 2025 hardness average is 199 mg/L, with samples ranging from 33 to 388 mg/L.
The City publishes separate reports for Modesto, Salida, Ceres, Del Rio, and other managed systems. This page uses the Modesto System report. Select the correct system before applying any number to your home.
A useful local question
Does the Modesto report also cover Salida and Ceres?
The City publishes separate reports for those systems. Match the system name on your bill and use its original report; this page’s measurements belong to the Modesto System.
Sources and methodology
We keep each utility’s results separate, show the reported sample year, and distinguish averages, maxima and tap-sampling percentiles. Hardness classifications use USGS ranges. Missing data stays unknown.
Different name on your water bill?
These local providers publish separate reports. Follow the matching utility link; the measurements above do not describe these systems.
- City of Modesto — Modesto System ↗2025 utility report; each result retains its measurement period
- USGS hardness classification
- EPA PFAS benchmarks and implementation
Sources checked November 15, 2026
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