Hard Water in Los Angeles County: Hardness by City, and What It Does to Your Appliances

What Hard Water Means and How It's Measured

Hardness is the amount of dissolved calcium and magnesium in your water, according to the U.S. Geological Survey (USGS). Utilities report it in one of two units: milligrams per liter (mg/L) as calcium carbonate, or grains per gallon (gpg). One grain per gallon equals 17.1 mg/L, so a utility that reports 171 mg/L is telling you about 10 gpg. This guide uses grains per gallon, the unit Whirlpool's dishwasher guidance uses.

The USGS scale sorts water into four bands. In mg/L as calcium carbonate: soft is 0 to 60, moderately hard is 61 to 120, hard is 121 to 180, and very hard is anything over 180. Converted to grains per gallon with the Nebraska Extension conversion, that's soft under 3.5, moderately hard 3.5 to 7, hard 7 to 10.5, and very hard over 10.5.

LA County Water Hardness by City and Water Provider

Here's the part most guides skip. A city name doesn't tell you what comes out of your tap, because many LA County cities are served by more than one water company. Two neighbors in Pico Rivera or Long Beach can be on different systems with very different numbers. The table lists the providers in seven LA County cities we serve.

Lowest on the list: Long Beach's Blended Zone at 4.4 gpg. Highest: Golden State Water's Norwalk system at 18 gpg. Find your provider's name on your water bill, then find its row.

Montebello is also served in part by California Water Service and South Montebello Irrigation District, which aren't listed here. Every figure is an average from that provider's own annual water quality report: for the whole system, or for each source where a row shows groundwater and imported water separately. Where a range is shown, it is the range the provider reported. Report years differ: the Downey and Montebello figures come from 2024 reports, the rest from 2025 or 2026 reports. Your tap water can vary from the average, so check the provider name on your water bill and look up its newest report.

Why Hardness Varies So Much Across the County

LA County water comes from two broad places. Imported water arrives through the Metropolitan Water District (MWD) from the Colorado River and the State Water Project. Local groundwater comes out of basins under the county, including the Central Basin, the Main San Gabriel Basin and the Raymond Basin. Each provider blends these in a different mix, and the mix decides the hardness.

Long Beach is a good example. Its groundwater treatment plant blends local and imported supply, and in 2025 the city's source mix was 71% local groundwater and 29% imported water. Its Blended Zone, which mixes treated groundwater with imported water, averaged 4.4 gpg in 2025. Its MWD Zone, which gets mostly imported water, averaged 12.8.

Both sources move from year to year. MWD's Weymouth plant averaged 234 mg/L (about 13.7 gpg) in 2025 and 272 mg/L (about 15.9 gpg) in 2024, so providers that lean on imported water shift with it. Groundwater moves too: Norwalk's city groundwater averaged 12.3 gpg in the 2024 report and 15.0 in the 2025 report. Long Beach's Blended Zone went the other way, from 5.4 gpg in 2023 to 4.4 in 2025. The point isn't the exact figure. It's that you should read your provider's newest report, not last year's.

What Hard Water Does to a Dishwasher

The dishwasher is where most people notice it first. The USGS notes that when hard water is heated, solid deposits of calcium carbonate can form. In a dishwasher that shows up as white film, spots and scale. Bosch, Samsung and Whirlpool all describe white residue or limescale on dishes and inside the tub as a hard water symptom.

Whirlpool's dishwasher help page goes further. It says extremely hard water, 15 grains per U.S. gallon or more, can damage a dishwasher and make good results hard to get, and it recommends a water softener at that level. That's Whirlpool's threshold, not a universal standard, but it's a useful yardstick against the table above. Golden State Water's Norwalk system (18), Downey (15.7), Norwalk's city groundwater (15.0), Pico Water District (14.8) and Whittier (14.6) all sit at or near that line. Long Beach's Blended Zone (4.4) and the Pico Rivera Water Authority (9.2) sit well below it.

Here's what manufacturers suggest doing about it:

• Use rinse aid. Whirlpool says liquid rinse aid helps drying and controls the buildup of hard water deposits, and it points out that not all detergent packs contain rinse aid.
• Set the hardness level, if your model has one. Some models have a built-in softener or a water-hardness setting, including certain Bosch, Miele, KitchenAid, Samsung and LG dishwashers. It's model-dependent, so check your manual. KitchenAid's help page says its softening system ships turned off (hardness setting 0) and tells owners to get their hardness from the water supplier's report, then fill the salt reservoir with dishwasher softener salt. LG says to use dishwasher salt, not table salt. Miele's manual says that if your hardness fluctuates, set the higher value.
• Read the unit chart. Brands don't agree on units. You'll see grains per gallon, degrees dH, mmol/L or ppm, so match your provider's figure to the chart in your manual.
• Descale now and then. Manufacturers point to a dishwasher cleaner or descaler. Whirlpool names affresh, and Samsung describes a vinegar cycle.

Refrigerator Ice Makers and Dispensers

White specks in your ice are the other common sign. Whirlpool says white particles in melting ice are minerals, usually calcium carbonate, and are a normal occurrence in hard water areas. It also strongly recommends not connecting an ice maker to softened water, since the salt can damage ice maker parts and affect taste.

A clogged filter is a separate problem. Whirlpool says a clogged water filter can reduce the flow to the ice maker and dispenser, GE says the same about flow to the ice maker, and Whirlpool recommends replacing its filter every 6 months or when the indicator light comes on. If your ice slows down or the dispenser dribbles, change the filter before assuming something worse.

When It's Not the Water: Getting a Repair in LA County

Scale doesn't explain every fault. If a dishwasher won't drain, a fridge stops making ice or a washer won't fill, we check filters, valves and the drain path first, then look at the water. Blaming the tap too early is a good way to replace the wrong part.

We cover Los Angeles County with one flat $99 service call, and same-day service is available. Our city pages cover the areas in this guide: Long Beach, Pico Rivera, Downey, Whittier and Montebello. In Pasadena, Beverly Hills, Santa Monica and Manhattan Beach we run a separate premium-brand service for Sub-Zero, Wolf, Miele, Thermador and similar; see our Pasadena premium appliance repair page. For a dishwasher that's leaving film behind or acting up, our dishwasher repair service is a good place to start.

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