Hardness
Soft to hard, depending on supply14–160mg/L as CaCO₃
range across treatment plants
USGS hardness classes
Walnut Creek, Lafayette and Orinda ranges are soft; Sobrante is moderately hard; Upper San Leandro is hard.
2025
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Your local water, explained
Alameda County Water Quality Report
EBMUD’s treatment-plant ranges show why one county hardness number would mislead.
EBMUD’s 2025 hardness ranges span 14–160 mg/L across treatment plants, from soft to hard. This guide covers its Alameda County service area and points to other utility reports; Alameda County Water District and other suppliers must be checked separately.
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Your water
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Check the supplier on your water bill. City and county boundaries can include several water systems.
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These are utility measurements, not a test at your tap or a current service advisory. Sources checked October 27, 2026
Choose the right utility report
The figures below are provider-specific. They are not a countywide average.
| Utility | Hardness | Hardness source |
|---|---|---|
| 14–160 mg/L as CaCO₃ · Soft to hard, depending on supply | 2025 · range across treatment plants |
Showing utility report
East Bay Municipal Utility District (EBMUD)
2025 utility report; measurement years are shown with each result
Use these results only if East Bay Municipal Utility District (EBMUD) supplies your home. County and ZIP boundaries do not confirm a water provider.
Your water at a glance
See the amount, the comparison and what it means. “Below” refers to the stated benchmark, not zero risk.
Chloramine
Below the 4 mg/L limit2.4mg/L as chlorine
highest running annual average
MRDL: 4 mg/L
Individual samples ranged 0.07–3.71 mg/L. Select treatment with a verified chloramine claim.
2025
View source ↗TTHMs
Below the 80 ppb limit57µg/L (ppb)
highest locational annual average
MCL: 80 ppb
Some individual samples reached 110 ppb. The compliance comparison uses locational running annual averages.
2025
View source ↗HAA5
Below the 60 ppb limit50µg/L (ppb)
highest locational annual average
MCL: 60 ppb
Individual samples reached 76 ppb. An individual sample and an annual average are different measures.
2025
View source ↗Fluoride
Below California’s 2 mg/L limit0.7mg/L
system average; samples 0.6–0.8
California MCL: 2 mg/L
Fluoride requires dedicated treatment if reducing it is a goal.
2025
View source ↗Lead
Below the report’s action levelND90th percentile
53 sampled homes
Report action level: 15 ppb
No samples exceeded 15 ppb; reported range ND–13.3 ppb. Home plumbing can change tap results.
2024
View source ↗Arsenic
Unknown, not zeroNot listedin the selected report tables
no numeric result shown
No comparison available
The absence of a value in these detected-contaminant tables does not establish your home’s arsenic level.
2025 report
View source ↗PFAS
Compound-specific findingsDetectedselected individual samples
PFHxA and PFBA in UCMR5 table
No single PFAS total
Selected plant samples contained PFHxA or PFBA even though the table’s system averages were ND. See the full report for context.
2025 report
View source ↗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 | 14–160 mg/L as CaCO₃range across treatment plants | 2025View source ↗ | Soft to hard, depending on supplyWalnut Creek, Lafayette and Orinda ranges are soft; Sobrante is moderately hard; Upper San Leandro is hard. |
| Chloramine | 2.4 mg/L as chlorinehighest running annual average | 2025View source ↗ | Below the 4 mg/L limitIndividual samples ranged 0.07–3.71 mg/L. Select treatment with a verified chloramine claim. |
| TTHMs | 57 µg/L (ppb)highest locational annual average | 2025View source ↗ | Below the 80 ppb limitSome individual samples reached 110 ppb. The compliance comparison uses locational running annual averages. |
| HAA5 | 50 µg/L (ppb)highest locational annual average | 2025View source ↗ | Below the 60 ppb limitIndividual samples reached 76 ppb. An individual sample and an annual average are different measures. |
| Fluoride | 0.7 mg/Lsystem average; samples 0.6–0.8 | 2025View source ↗ | Below California’s 2 mg/L limitFluoride requires dedicated treatment if reducing it is a goal. |
| Lead | ND 90th percentile53 sampled homes | 2024View source ↗ | Below the report’s action levelNo samples exceeded 15 ppb; reported range ND–13.3 ppb. Home plumbing can change tap results. |
| Arsenic | Not listed in the selected report tablesno numeric result shown | 2025 reportView source ↗ | Unknown, not zeroThe absence of a value in these detected-contaminant tables does not establish your home’s arsenic level. |
| PFAS | Detected selected individual samplesPFHxA and PFBA in UCMR5 table | 2025 reportView source ↗ | Compound-specific findingsSelected plant samples contained PFHxA or PFBA even though the table’s system averages were ND. See the full report for context. |
| Hardness — Walnut Creek | 15–21 mg/L as CaCO₃plant sample range | 2025View source ↗ | SoftPlant-associated samples may include water from another plant; confirm your current blend. |
| Hardness — Lafayette | 14–27 mg/L as CaCO₃plant sample range | 2025View source ↗ | SoftPlant-associated samples may include water from another plant; confirm your current blend. |
| Hardness — Orinda | 14–40 mg/L as CaCO₃plant sample range | 2025View source ↗ | SoftPlant-associated samples may include water from another plant; confirm your current blend. |
| Hardness — Sobrante | 64–98 mg/L as CaCO₃plant sample range | 2025View source ↗ | Moderately hardPlant-associated samples may include water from another plant; confirm your current blend. |
| Hardness — Upper San Leandro | 140–160 mg/L as CaCO₃plant sample range | 2025View source ↗ | HardPlant-associated samples may include water from another plant; confirm your current blend. |
| PFHxA — Upper San Leandro | ND–3.4 ng/L (ppt)individual sample range | 2025 reportView source ↗ | Below report’s 1,000 ppt notification levelUCMR5 result; the notification level is not an MCL. |
| PFBA — Upper San Leandro | ND–5.2 ng/L (ppt)individual sample range | 2025 reportView source ↗ | No benchmark listed in this tableSobrante range was ND–5.1 ppt; other listed plants were ND. |
| Chlorate | 108 µg/L (ppb)system average | 2025View source ↗ | Below report’s 800 ppb notification levelA notification level is not an enforceable MCL. |
| NDMA | 3.9 ng/L (ppt)highest locational annual average | 2025View source ↗ | Below report’s 10 ppt notification levelHighest individual sample in the table was 6.5 ppt. |
| Total dissolved solids | 65 mg/Lsystem average | 2025View source ↗ | Below the 500 mg/L secondary limitTDS describes dissolved material collectively; it is not a contaminant-specific test. |
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. Sierra Nevada water from the Mokelumne River and water from East Bay reservoirs. Plant supplies and seasonal blends affect hardness.
Your provider needs its own report.
Continue with your home details for general filtration guidance. We will not use another utility’s numbers as your result.
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What this means for your home
Alameda County is a geographic boundary, not one water system. This page uses EBMUD data for its service area, including Oakland; do not apply it automatically to Fremont, Newark, Union City or another utility’s customers. EBMUD’s plant-associated samples can also reflect blended supplies, so the full system range is not a measurement of your household.
Related city reports
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.
A useful local question
Is Alameda County’s water hard or soft?
It depends on your utility and source. EBMUD reports soft ranges at Walnut Creek, Lafayette and Orinda, moderately hard water at Sobrante and hard water at Upper San Leandro. Confirm the supply serving your home before selecting a softener. A filter for chloramine addresses a different goal from hardness reduction.
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.
- East Bay Municipal Utility District (EBMUD) ↗2025 utility report; measurement years are shown with each result
- EBMUD water quality and original annual reports ↗
- USGS hardness classification
- EPA PFAS benchmarks and implementation
Sources checked October 27, 2026
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