Hardness
Very hard at City plants237–243mg/L as CaCO₃
Range of three City plant averages
USGS: very hard >180 mg/L
Purchased treated water averages 145 mg/L (hard) and has a wider range. See each supply below.
2025
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San Diego County water reports & provider guide
Start with City of San Diego data, or follow your own district’s report.
The detailed results below belong to the City of San Diego system. Its three City plant averages are very hard, while purchased treated water differs. Neighboring districts need their own data.
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These are utility measurements, not a test at your tap or a current service advisory. Sources checked October 25, 2026
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The figures below are provider-specific. They are not a countywide average.
| Utility | Hardness | Hardness source |
|---|---|---|
| 237–243 mg/L · Very hard at City plants | 2025 reported hardness |
Showing utility report
City of San Diego Public Utilities Department
2025 utility report; each result retains its sampling year
Only use these results if City of San Diego Public Utilities Department is the supplier on your bill. Other utilities and private wells need their own data.
Your water at a glance
See the amount, the comparison and what it means. “Below” refers to the stated benchmark, not zero risk.
Disinfectant residual
Below 4 mg/L MRDL1.75mg/L
Chloramines · distribution average
Range: ND–3.80 mg/L. Choose filtration with verified chloramine performance.
2025
View source ↗TTHM
Below 80 ppb MCL55ppb
Maximum locational running annual average
Individual samples are not the annual-average compliance result.
2025
View source ↗HAA5
Below 60 ppb MCL15ppb
Maximum locational running annual average
Individual samples are not the annual-average compliance result.
2025
View source ↗Fluoride
Below California 2 mg/L MCL0.6–0.8mg/L
Range of final-water plant averages
Full final-water range: 0.2–0.9 mg/L. Natural and final-water fluoride rows are not added together.
2025
View source ↗Lead
Below 15 ppb action levelND (<5)ppb
90th percentile · 56 sampled taps
0 of 56 sites exceeded the action level. Your plumbing can affect your tap.
2023
View source ↗Arsenic
Below reporting limitND (<2)ppb
Supplementary nondetect list
Not detected is not zero; MCL 10 ppb differs from the 0.004 ppb health goal.
2025
View source ↗PFAS — PFBA
Detected; no MCL listed5.4ppt
Alvarado average · range ND–7.0
Other plant averages were ND. Do not compare PFBA to PFOA/PFOS limits.
2025
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.
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| What was measured | Reported amount | Sample year / source date | How to read it |
|---|---|---|---|
| Hardness | 237–243 mg/L as CaCO₃Range of three City plant averages | 2025View source ↗ | Very hard at City plantsPurchased treated water averages 145 mg/L (hard) and has a wider range. See each supply below. |
| Disinfectant residual | 1.75 mg/LChloramines · distribution average | 2025View source ↗ | Below 4 mg/L MRDLRange: ND–3.80 mg/L. Choose filtration with verified chloramine performance. |
| TTHM | 55 ppbMaximum locational running annual average | 2025View source ↗ | Below 80 ppb MCLIndividual samples are not the annual-average compliance result. |
| HAA5 | 15 ppbMaximum locational running annual average | 2025View source ↗ | Below 60 ppb MCLIndividual samples are not the annual-average compliance result. |
| Fluoride | 0.6–0.8 mg/LRange of final-water plant averages | 2025View source ↗ | Below California 2 mg/L MCLFull final-water range: 0.2–0.9 mg/L. Natural and final-water fluoride rows are not added together. |
| Lead | ND (<5) ppb90th percentile · 56 sampled taps | 2023View source ↗ | Below 15 ppb action level0 of 56 sites exceeded the action level. Your plumbing can affect your tap. |
| Arsenic | ND (<2) ppbSupplementary nondetect list | 2025View source ↗ | Below reporting limitNot detected is not zero; MCL 10 ppb differs from the 0.004 ppb health goal. |
| PFAS — PFBA | 5.4 pptAlvarado average · range ND–7.0 | 2025View source ↗ | Detected; no MCL listedOther plant averages were ND. Do not compare PFBA to PFOA/PFOS limits. |
| Nitrate as nitrogen | ND mg/L as NAll plant averages · largest sample 0.5 | 2025View source ↗ | Below 10 mg/L MCLND is below the reporting limit. |
| PFOA and PFOS | ND (<2) pptSupplementary nondetect list | 2025View source ↗ | Below reporting limitsDoes not erase the separate PFBA detection. |
| Hardness — Alvarado | 237 mg/L as CaCO₃Average · range 203–270 | 2025View source ↗ | very hardCalculated average: 13.8 gpg. |
| Hardness — Miramar | 242 mg/L as CaCO₃Average · range 200–285 | 2025View source ↗ | very hardCalculated average: 14.1 gpg. |
| Hardness — Otay | 243 mg/L as CaCO₃Average · range 201–271 | 2025View source ↗ | very hardCalculated average: 14.2 gpg. |
| Hardness — Purchased treated water | 145 mg/L as CaCO₃Average · range 54.4–232 | 2025View source ↗ | hard average; range spans soft through very hardCalculated average: 8.5 gpg. |
| TDS — Alvarado | 532 mg/LAverage · range 434–590 | 2025View source ↗ | Below 1,000 mg/L secondary MCLAesthetic benchmark; this does not measure hardness. |
| TDS — Miramar | 533 mg/LAverage · range 474–611 | 2025View source ↗ | Below 1,000 mg/L secondary MCLAesthetic benchmark; this does not measure hardness. |
| TDS — Otay | 585 mg/LAverage · range 508–634 | 2025View source ↗ | Below 1,000 mg/L secondary MCLAesthetic benchmark; this does not measure hardness. |
| TDS — Purchased treated water | 361 mg/LAverage · range 105–513 | 2025View source ↗ | Below 1,000 mg/L secondary MCLAesthetic benchmark; this does not measure hardness. |
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 ↗
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Source water. Mostly imported Colorado River/State Water Project blends. City plants: Alvarado, Miramar, Otay. A smaller purchased treated-water supply blends Skinner, Twin Oaks Valley and Carlsbad desalination sources. Do not confuse City Otay plant with Otay Water District.
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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More about your local water
What this means for your home
City of San Diego water and neighboring districts are separate systems. The City’s Otay treatment plant is not Otay Water District. Purchased treated water also has a different hardness profile.
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
Can I use one report for all of San Diego County?
No. The detailed figures here belong only to City of San Diego Public Utilities Department. Use the other-provider links for a different supplier, and current testing for a private well.
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.
- City of San Diego Public Utilities Department ↗2025 utility report; each result retains its sampling year
- 2025 nondetected parameters supplement ↗
- USGS hardness classification
- EPA PFAS benchmarks and implementation
Sources checked October 25, 2026
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