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Water Hardness in California Cities

Water hardness, indicated by the level of dissolved minerals such as calcium and magnesium, varies across the diverse landscapes of California. Situated along the western coast of the U.S., California’s water hardness levels are highly variable, reflecting the complex geological makeup of the state.

In California, the water hardness can range from very soft in certain areas to extremely hard in others, mirroring the varied geology and the sources of the state’s water. For example, regions with rapid runoff from mountain snowmelt, like those in the Sierra Nevada, typically have softer water because the water has limited interaction with mineral-rich soils or rocks. On the other hand, areas with a great deal of sedimentary rock, such as parts of the Central Valley, may have harder water due to higher concentrations of dissolved minerals like calcium and magnesium.

These differences in water hardness across California not only affect the taste of the water but also have implications for the performance of soaps and detergents. Additionally, there is an impact on the maintenance of plumbing systems and the longevity of household appliances. Given California’s vast size and geological diversity, water hardness levels are far from consistent and can change markedly, underscoring the importance of localized water treatment methods and continual water quality monitoring.

The data provided demonstrates a range of water hardness levels across various cities in California, measured in parts per million (ppm) and Grains Per Gallon (gpg). For example, Santa Clarita and Oxnard have particularly high water hardness levels, reaching upwards of 437.5 ppm, 25.53 gpg. In contrast, cities such as San Francisco and Anaheim report remarkably soft water, with measurements as low as 18.0 ppm, 1.05 gpg. There is, however, a noteworthy lack of water hardness data for certain areas including Elk Grove and Rancho Cucamonga, as no current figures are available for these cities.

CityHardness ppm (mg/L)Hardness gpgInformation SourceNotes
Los Angeles195.011.4LinkTook mean of six sources
San Diego260.715.2LinkTook mean of three treatment plants
San Jose238.213.9LinkTook mean of six treatment plants
San Francisco32.01.9Link
Long Beach121.07.1LinkUsed the “Blended Zone” number which includes water purchased from other systems and distributed through LB
Oakland63.83.7LinkTook mean of three treatment plants serving Oakland city
Bakersfield68.44.0LinkTook mean of two listed sources
Stockton92.05.4LinkTook mean of two listed sources
Santa Ana248.014.5Link
Irvine226.013.2LinkTook mean of three listed sources
Chula Vista220.812.9Link
Fremont148.08.6LinkTook blended water average
Santa Clarita420.024.5LinkTook only Santa Clarita Water Division from SCV Water Report
San Bernardino249.414.6Link
Moreno Valley197.311.5LinkTook mean of four listed sources for Moreno Valley area
Huntington Beach161.09.4Link
Glendale360.321.0LinkTook mean of seven listed sources for Glendale
Elk Groven/an/aLinkCorrupted PDF files for last 3 years of CCRs when checked
Ontario138.08.1LinkTook mean of two listed sources
Santa Rosa112.06.5Link
Rancho Cucamongan/an/aLinkWebsite Down when checked
Oceanside218.812.8LinkTook mean of five listed sources
Garden Grove265.015.5Link
Lancaster82.54.8LinkTook mean of two listed sources
Palmdale115.06.7LinkTook mean of two listed sources
Corona162.09.5LinkUsed treated average system water value
Sunnyvale144.38.4LinkTook mean of three listed source
Roseville78.54.6LinkTook mean of two listed sources
Pomona199.811.7LinkTook mean of four listed sources
Torrance211.012.3LinkPurchases from Metro Water Dist. of SoCal Took average of 5 sources, not clear what the exact blend was for Torrance
Santa Clara296.017.3Link
Simi Valley280.016.4Link
Thousand Oaks140.48.2LinkUsed weighted mean of the two sources that account for 92% of supply, although others are listed
Concord119.07.0LinkPart of Contra Costa Water District
Berkeley63.83.7LinkSame water district as Oakland, used those numbers
Richmond63.83.7LinkSame water district as Oakland, used those numbers
Antioch110.06.4LinkTook mean of two sources
Temecula218.512.8LinkUses Rancho California Water (https://temeculaca.gov/754/Utilities)
Costa Mesa278.516.3Link
San Buenaventura (Ventura)479.028.0LinkTook mean of three sources
Santa Maria275.016.1LinkTook mean of two “Blend” values
West Covina280.016.4LinkWest Covina uses multiple water sources, took the Covina report as that’s the closest city geographically (https://www.westcovina.org/departments/community-development/engineering-division/water-utilities-emergency-numbers)
Jurupa Valley168.09.8Link
El Monte260.015.2Link
Menifee197.311.5LinkSame system as Moreno Valley
El Cajon238.014.0LinkEl Cajon served by Helix Water (https://www.elcajon.gov/your-government/departments/public-works/utilities/other-utilities)
Rialto158.09.2LinkUsed City of Rialto number only
San Mateo34.02.0Link
Daly City32.01.9Link
Vista214.412.5LinkTook mean of five sources
Tracy143.08.4LinkTook mean of three sources
San Marcos226.713.2Link
Carson171.510.0LinkServed by Rancho Domingo
Redding70.34.1LinkTook mean of two sources
Chino170.910.0LinkTook mean of three sources
Mission Viejo278.016.2LinkCovered by Santa Margarita Water District (https://cityofmissionviejo.org/water-conservation)
South Gate227.113.3Link
Santa Monica277.316.2LinkTook mean of listed sources
San Leandro63.83.7LinkCovered under same district as Oakland
Santa Barbara287.016.8Link
Citrus Heights74.04.3Link
San Ramon235.013.7Link
Lake Forest278.016.2LinkCovered by El Toro Water District
Newport Beach278.016.2Link
Top 100 California cities by population and their reported water hardness
ppm = Parts Per Million
mg/L = Milligrams Per Liter
gpg = Grains Per Gallon

Hard water can cause issues such as mineral buildup in plumbing and appliances, reduce the efficacy of soaps and detergents, and affect the taste of the water. A tried and true solution is the use of a water softener. A water softener, like the ones from DROP, could be a worthwhile investment.

These devices work by replacing the calcium and magnesium ions that cause hardness with sodium ions, resulting in softer water. With innovative features, easy installation, and efficient operation, DROP smart water softeners provide a solution to hard water issues, extending the lifespan of appliances, improving water taste, enhancing soap effectiveness, reducing scale build-up, and increasing the overall water efficiency in your home.

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