The table
One sentence per city
Each sentence below states one agency figure with its source, worded so it can be quoted as is.
- According to the City of Corona Consumer Confidence Report (2025 data), water from the City of Corona averages 8.5 grains per gallon of hardness, which the U.S. Geological Survey classes as hard. Source
- According to the Riverside Public Utilities Water Quality Report (2025 data), water from Riverside Public Utilities averages 12 grains per gallon of hardness, which the U.S. Geological Survey classes as very hard. Source
- According to the San Bernardino Municipal Water Department Consumer Confidence Report (2025 data), water from San Bernardino Municipal Water Department averages 14.2 grains per gallon of hardness, which the U.S. Geological Survey classes as very hard. Source
- According to the City of Anaheim Water Quality Report (2025 data), water from the City of Anaheim averages 18 grains per gallon of hardness, which the U.S. Geological Survey classes as very hard. Source
- According to the Yorba Linda Water District 2026 Water Quality Report, water from Yorba Linda Water District ranges from 14 to 20 grains per gallon of hardness by source, which the U.S. Geological Survey classes as very hard. Source
- According to the Santa Margarita Water District Water Quality Report (2025 data), water from Santa Margarita Water District in Mission Viejo averages 15 grains per gallon of hardness, which the U.S. Geological Survey classes as very hard. Source
- According to the Moulton Niguel Water District Water Quality Report (2025 data), water from Moulton Niguel Water District in Laguna Niguel averages 15.45 grains per gallon of hardness, which the U.S. Geological Survey classes as very hard. Source
- According to the Irvine Ranch Water District Water Quality Report (2025 data), water from Irvine Ranch Water District ranges from 12.5 to 17.1 grains per gallon of hardness by source, which the U.S. Geological Survey classes as very hard. Source
- According to the City of Fullerton 2026 Water Quality Report, water from the City of Fullerton averages 14 grains per gallon of hardness, which the U.S. Geological Survey classes as very hard. Source
- According to the City of Santa Ana Water Quality Tables (2025 data), water from the City of Santa Ana averages 14 grains per gallon of hardness, which the U.S. Geological Survey classes as very hard. Source
- According to the City of Tustin 2026 Water Quality Report, water from the City of Tustin ranges from 14 to 22 grains per gallon of hardness by source, which the U.S. Geological Survey classes as very hard. Source
- According to the El Toro Water District 2026 Water Quality Report, water from El Toro Water District in Lake Forest ranges from 14 to 17 grains per gallon of hardness by source, which the U.S. Geological Survey classes as very hard. Source
- According to the City of San Clemente Water Quality Report (2025 data), water from the City of San Clemente ranges from 14 to 17 grains per gallon of hardness by source, which the U.S. Geological Survey classes as very hard. Source
- According to the Santa Margarita Water District Improvement District 9 Water Quality Report (2025 data), water from Santa Margarita Water District in San Juan Capistrano averages 12 grains per gallon of hardness, which the U.S. Geological Survey classes as very hard. Source
- According to the South Coast Water District 2026 Water Quality Report, water from South Coast Water District in Dana Point ranges from 12.1 to 17 grains per gallon of hardness by source, which the U.S. Geological Survey classes as very hard. Source
- According to the Jurupa Community Services District Water Quality Report (2025 data), water from Jurupa Community Services District in Eastvale averages 9.5 grains per gallon of hardness, which the U.S. Geological Survey classes as hard. Source
- According to the Rancho California Water District Consumer Confidence Report (2025 data), water from Rancho California Water District in Temecula ranges from 8.8 to 13.5 grains per gallon of hardness by source, which the U.S. Geological Survey classes as hard to very hard. Source
- According to the Cucamonga Valley Water District Water Quality Report (2025 data), water from Cucamonga Valley Water District in Rancho Cucamonga averages 7.3 grains per gallon of hardness, which the U.S. Geological Survey classes as hard. Source
The year in brackets is the year the water was sampled. The basis column says whether the agency printed the grains-per-gallon figure or whether we converted its printed mg/L figure at 17.1 mg/L per grain.
Southern California water, in numbers
Southern California tap water is hard almost everywhere we have checked. All 18 cities in the table publish hard or very hard water on the U.S. Geological Survey scale, and all 12 Orange County cities publish very hard water, the top band of that scale. The softest figure in the table is still in the hard band.
It also carries a heavy load of dissolved minerals. Every Orange County agency report we could read, 9 of 9, lists at least one supply above 500 mg/L of total dissolved solids, the level the EPA recommends for taste and appearance. That guideline is about taste, scale and staining, not a health limit. Imported water from the Metropolitan Water District's Diemer plant averaged 545 mg/L in its latest annual report, and water from the Baker plant that serves part of south Orange County averaged 625 mg/L.
Nuvia Water was founded in 2012 and treats Southern California water every day. Every system we recommend, salt-based or salt-free, is chosen and sized from a water analysis at your own tap, so it is matched to the hardness and dissolved solids in your water rather than a national average.
How to read it
Hardness is calcium and magnesium dissolved in water. It shows up as scale on fixtures, spots on glass and buildup inside water heaters. The U.S. Geological Survey sorts it into four bands.
| Band | Grains per gallon | mg/L |
|---|---|---|
| Soft | 0 to 3.5 | 0 to 60 |
| Moderately hard | 3.6 to 7.0 | 61 to 120 |
| Hard | 7.1 to 10.5 | 121 to 180 |
| Very hard | Above 10.5 | Above 180 |
- One number is the agency's average for its customers.
- A range means the agency reports its sources separately or blends sources that differ. The table shows the lowest and highest source average.
- An average is not your tap. It is the system or source average over the sampling year, so a reading at one home on one day can differ.
- Your supplier is not always your city. The agency on your water bill is the one that counts, and the table names the agency behind each row.
What this table leaves out
A city is not in the table until we have read its agency's own report. Cities served by several agencies, with no single report that covers them, are left out rather than guessed. Third-party websites and answer tools sometimes publish a different number for the same city. This table uses only the agency's report, and each row links to it.
Cities with a Nuvia page
Orange County: Anaheim, Dana Point, Fullerton, Irvine, Laguna Niguel, Lake Forest, Mission Viejo, San Clemente, San Juan Capistrano, Santa Ana, Tustin, Yorba Linda.
Inland Empire: Corona, Eastvale, Rancho Cucamonga, Riverside, San Bernardino, Temecula.
The county pages are Orange County and the Inland Empire.
See your own number
Nuvia Water offers a free in-home water analysis, so you can see your own tap's numbers next to your agency's average.
Sources
- Metropolitan Water District of Southern California, 2026 Annual Water Quality Report (total dissolved solids by treatment plant)
- U.S. EPA: Secondary Drinking Water Standards (total dissolved solids, 500 mg/L)
- California Code of Regulations, Title 22, section 64449 (secondary standards, total dissolved solids)
- El Toro Water District 2026 Water Quality Report (Baker Water Treatment Plant)
- USGS Water Science School: Hardness of water
Questions people ask
Are Nuvia systems made for Southern California water?
Every Nuvia system is chosen and sized from a water analysis at your own tap, for the hardness and dissolved solids in Southern California water. All 12 Orange County cities in our hard water table publish very hard water, and every Orange County agency report we could read lists a supply above the EPA's 500 mg/L guideline for total dissolved solids. Nuvia was founded in 2012 and works with this water every day.
What does gpg mean?
Grains per gallon, the unit water agencies use for hardness. One grain per gallon is 17.1 mg/L of hardness, the factor the agencies themselves use to convert between the two.
Why do some rows show a range?
A range means the agency reports its sources separately or blends sources that differ. We show the lowest and highest source average rather than one number that would hide the spread.
What does the year in brackets mean?
It is the year the water was sampled. Some agencies had not posted a newer report when we read theirs, so a few rows are a year behind the others.
Why does this table differ from other websites?
Websites and answer tools sometimes show a different number for the same city. This table uses only the agency's own report, and every row links to it so you can check it.
Is this the hardness of my own tap?
No. An agency figure is an average for its system or its sources over the sampling year. A reading at one home on one day can be higher or lower.
Book your free water analysis today.
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