Your local water, explained
Find your retailer first. Hardness can change dramatically with the water source.
San Jose Water’s 2025 report shows source hardness averages from 99 to 288 mg/L: moderately hard to very hard. This county guide starts with that utility’s main system and links to other local suppliers; it does not assign one result to all of Santa Clara County.
Your water → your home → your system
Your water
Check the supplier on your water bill. City and county boundaries can include several water systems.
Only the listed water system is summarized here. Choose “Other / not sure” if your bill shows a different supplier.
Confirm the provider on your bill, or choose “Other / not sure” to continue without a matched report.
These are utility measurements, not a test at your tap or a current service advisory. Sources checked October 27, 2026
The figures below are provider-specific. They are not a countywide average.
| Utility | Hardness | Hardness source |
|---|---|---|
| 99–288 mg/L as CaCO₃ · Moderately hard to very hard | 2025 · range of three source averages |
2025 utility report; measurement years are shown with each result
Use these results only if San Jose Water — main system supplies your home. County and ZIP boundaries do not confirm a water provider.
See the amount, the comparison and what it means. “Below” refers to the stated benchmark, not zero risk.
99–288mg/L as CaCO₃
range of three source averages
USGS hardness classes
Source averages: Valley Water 99, mountain water 151, groundwater 288. Full reported range: 77–451. This is not a home measurement.
2025
View source ↗1.42mg/L
running annual average
MRDL: 4 mg/L
The utility uses chlorine and chloramine. Ask for filtration suited to both disinfectants.
2025
View source ↗47.7µg/L (ppb)
highest site average
MCL: 80 ppb
Disinfection byproduct result; compliance uses the prescribed site average, not an individual tap result.
2025
View source ↗27.3µg/L (ppb)
highest site average
MCL: 60 ppb
Haloacetic acids are disinfection byproducts. The annual report gives the sampling context.
2025
View source ↗0.75mg/L
treated Valley Water average
California MCL: 2 mg/L
Other source averages differ: groundwater 0.10 mg/L; mountain source not detected. Standard filtration is not dedicated fluoride treatment.
2025
View source ↗1.6–2.1µg/L (ppb)
fall / spring 90th percentiles
Report action level: 15 ppb
One sampled home in each round exceeded 15 ppb. A system percentile does not establish the lead level in your home.
2025
View source ↗ND–2.2µg/L (ppb)
groundwater sample range
MCL: 10 ppb
Groundwater average was not detected. ND means below the reporting threshold, not zero.
2025
View source ↗Detectedsource monitoring
includes offline wells
Compound-specific results
The report includes wells that were not supplying customers. These detections are not a measurement of water at your tap.
2025
View source ↗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 | 99–288 mg/L as CaCO₃range of three source averages | 2025View source ↗ | Moderately hard to very hardSource averages: Valley Water 99, mountain water 151, groundwater 288. Full reported range: 77–451. This is not a home measurement. |
| Total chlorine | 1.42 mg/Lrunning annual average | 2025View source ↗ | Below the 4 mg/L limitThe utility uses chlorine and chloramine. Ask for filtration suited to both disinfectants. |
| TTHMs | 47.7 µg/L (ppb)highest site average | 2025View source ↗ | Below the 80 ppb limitDisinfection byproduct result; compliance uses the prescribed site average, not an individual tap result. |
| HAA5 | 27.3 µg/L (ppb)highest site average | 2025View source ↗ | Below the 60 ppb limitHaloacetic acids are disinfection byproducts. The annual report gives the sampling context. |
| Fluoride | 0.75 mg/Ltreated Valley Water average | 2025View source ↗ | Below California’s 2 mg/L limitOther source averages differ: groundwater 0.10 mg/L; mountain source not detected. Standard filtration is not dedicated fluoride treatment. |
| Lead | 1.6–2.1 µg/L (ppb)fall / spring 90th percentiles | 2025View source ↗ | Below the report’s action levelOne sampled home in each round exceeded 15 ppb. A system percentile does not establish the lead level in your home. |
| Arsenic | ND–2.2 µg/L (ppb)groundwater sample range | 2025View source ↗ | Below the 10 ppb limitGroundwater average was not detected. ND means below the reporting threshold, not zero. |
| PFAS | Detected source monitoringincludes offline wells | 2025View source ↗ | Source context mattersThe report includes wells that were not supplying customers. These detections are not a measurement of water at your tap. |
| Hardness — mountain source | 151 mg/L as CaCO₃source average | 2025View source ↗ | HardAbout 8.8 grains per gallon, calculated using mg/L ÷ 17.1. |
| Hardness — groundwater | 288 mg/L as CaCO₃average; range 175–451 | 2025View source ↗ | Very hard averageAbout 16.8 grains per gallon. Supports a softener recommendation when this supply serves the home. |
| Hardness — Valley Water | 99 mg/L as CaCO₃average; range 77–146 | 2025View source ↗ | Moderately hard averageAbout 5.8 grains per gallon; the upper end reaches the hard category. |
| Chromium-6 — groundwater | 4.67 µg/Laverage; range 0.74–8.54 | 2025View source ↗ | Below the 10 µg/L limitThe report’s health goal is 0.02 µg/L; a health goal differs from an enforceable MCL. |
| Nitrate as nitrogen — groundwater | 3.1 mg/Laverage; range 0.61–6.5 | 2025View source ↗ | Below the 10 mg/L limitNitrate treatment needs a verified treatment claim; a softener is not nitrate treatment. |
| Bromate — Valley Water | 1.5 µg/Laverage; range ND–5.4 | 2025View source ↗ | Below the 10 µg/L limitResult applies to the treated Valley Water source. |
| Total dissolved solids | 200 / 397 / 247 mg/Lmountain / groundwater / Valley averages | 2025View source ↗ | Below report’s 1,000 mg/L secondary limitTDS is not a measurement of any one contaminant. |
| PFHxS — groundwater | ND–9.8 ng/L (ppt)source range; includes offline wells | 2025View source ↗ | Some samples above the 3 ppt notification levelIncludes wells not supplying customers. A notification level is not an MCL. |
| PFOA — groundwater | ND–4.6 ng/L (ppt)source range; includes offline wells | 2025View source ↗ | Some samples above the 4 ppt notification levelDo not interpret the maximum as a home’s exposure. |
| PFOS — groundwater | ND–9.7 ng/L (ppt)source range; includes offline wells | 2025View source ↗ | Some samples above the 4 ppt notification levelAsk the utility about the current source blend and treatment; check exact model reduction claims. |
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 ↗
Choose the system size, keep useful existing equipment, and review your filtration goals.
Source water. Local mountain surface water, groundwater and treated surface water supplied by Valley Water. The source blend can change by location and season.
Continue with your home details for general filtration guidance. We will not use another utility’s numbers as your result.
Find My Water System →A city report cannot establish a well’s water quality. Well-water treatment depends on your test results and site conditions.
Explore well-water systems →Email delivery is coming soon. Copy the report link to share it now.
More about your local water
Santa Clara County has multiple retailers and a mix of groundwater and treated surface water. A county or ZIP code cannot identify the blend at your tap. Check the name on your bill and use Valley Water’s retailer finder if needed. For San Jose Water customers, the groundwater average supports softening for scale control, while the softer Valley Water supply calls for a more specific home assessment.
These local providers publish separate reports. Follow the matching utility link; the measurements above do not describe these systems.
A useful local question
No single county average answers that. San Jose Water reports 288 mg/L for groundwater, 151 mg/L for mountain water and 99 mg/L for treated Valley Water. We recommend a softener for a home receiving hard water; a current hardness test helps select the settings. Keep chlorine and chloramine filtration as a separate treatment decision.
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.
Sources checked October 27, 2026
Your water → your home → your system
Choose the system size, keep useful existing equipment, and review your filtration goals.