Does your Orange County city have hard water?
Updated . By the OakTend team.
Which Orange County cities have hard water?
Find your city, then check the provider name on your water bill. Ratings use the Water Quality Association's scale, explained below, on each provider's 2025 average.
Groundwater: 18 grains per gallon, very hard
Imported water treated at the Lenain plant: 17 grains per gallon, very hard
Groundwater: 6.6 grains per gallon, moderately hard
Mesa Water serves most of the city; Irvine Ranch Water District serves part.
Local groundwater: 13 grains per gallon, very hard
Groundwater: 18 grains per gallon, very hard
Groundwater: 10 grains per gallon, hard
Local groundwater: 12.5 grains per gallon, very hard
Local surface water: 17.1 grains per gallon, very hard
Local groundwater: 12.5 grains per gallon, very hard
Local surface water: 17.1 grains per gallon, very hard
The district serves most of Lake Forest.
Groundwater: 14 grains per gallon, very hard
Mesa Water and Irvine Ranch Water District serve parts of the city.
All sources: 18 grains per gallon, very hard
Irvine Ranch Water District serves part of the city.
Groundwater: 14 grains per gallon, very hard
City groundwater: 22 grains per gallon, very hard
East Orange County Water District groundwater: 20 grains per gallon, very hard
Irvine Ranch Water District serves part of the city.
City limits and water service areas do not always line up, as the notes for Costa Mesa, Newport Beach, Orange and Tustin show. Golden State Water's three systems and Santa Margarita Water District are in the provider table below, but their reports do not name the cities they serve, so they have no city row. Every city is on the Orange County hub.
How hard is the water from each Orange County provider?
Averages for 2025, as each provider printed them. Where a provider listed more than one local source, each gets its own line; imported water appears once, below the table. The range is the lowest and highest reading in the report.
Anaheim Public Utilities
Groundwater: 18 grains per gallon, 316 mg/L
Imported water treated at the Lenain plant: 17 grains per gallon, 298 mg/L
Range: 162 to 431 mg/L
Groundwater served over 80 percent of customers in 2025.
City of Fountain Valley
Local groundwater: 13 grains per gallon, 217 mg/L
Range: 171 to 256 mg/L
The city did not import any water in 2025.
City of Garden Grove
Groundwater: 18 grains per gallon, 303 mg/L
Range: 187 to 346 mg/L
Golden State Water, Cowan Heights system
Source water: 13.8 grains per gallon, 236 mg/L
Range: 191 to 280 mg/L
Golden State Water, Placentia-Yorba Linda system
Source water: 11 grains per gallon, 188 mg/L
Range: 67.1 to 299 mg/L
Golden State Water, West Orange County system
Source water: 13.8 grains per gallon, 237 mg/L
Range: 62.9 to 369 mg/L
City of Huntington Beach
Groundwater: 10 grains per gallon, 162 mg/L
Range: 58.9 to 280 mg/L
About 85 percent groundwater and 15 percent imported water in 2025.
Irvine Ranch Water District
Local groundwater: 12.5 grains per gallon, 214 mg/L
Local surface water: 17.1 grains per gallon, 293 mg/L
Range: 52 to 469 mg/L
Mesa Water District
Groundwater: 6.6 grains per gallon, 113 mg/L
Range: 20.6 to 293 mg/L
All local groundwater.
City of Newport Beach
Groundwater: 14 grains per gallon, 232 mg/L
Range: 47.5 to 475 mg/L
About 85 percent groundwater and 15 percent imported water.
City of Orange
All sources: 18 grains per gallon, 300 mg/L
Range: 130 to 380 mg/L
City of Santa Ana
Groundwater: 14 grains per gallon, 239 mg/L
Range: 130 to 307 mg/L
About 85 percent groundwater and 15 percent imported water.
Santa Margarita Water District
Water delivered: 15 grains per gallon, 256 mg/L
Range: 210 to 300 mg/L
Imported water, part of it treated at Irvine Ranch Water District's Baker plant.
City of Tustin
City groundwater: 22 grains per gallon, 377 mg/L
East Orange County Water District groundwater: 20 grains per gallon, 333 mg/L
Range: 133 to 609 mg/L
Imported water from the Metropolitan Water District, which most of these providers buy some of, averaged 234 to 236 mg/L, or about 14 grains per gallon, in the reports that list it.
Each provider name links to its report. Every report printed both units, so nothing here is converted by us. City of Orange's report is the copy filed with the State Water Resources Control Board. If your provider is missing, we have not read its report yet. You are welcome to cite this table; please link back to this page.
How do grains per gallon and mg/L compare?
They measure the same thing: dissolved calcium and magnesium, counted as calcium carbonate. One grain per gallon equals 17.1 mg/L, and mg/L is the same number as parts per million (ppm). On the Water Quality Association's scale, under 1 grain per gallon is soft, 1 to 3.5 is slightly hard, 3.5 to 7 is moderately hard, 7 to 10.5 is hard, and over 10.5, about 180 mg/L, is very hard.
Do Huntington Beach and Irvine have hard water?
Yes, both. In Huntington Beach, the city's own groundwater, most of its supply, rates hard, and the imported water it blends in rates very hard.
Irvine gets its water from Irvine Ranch Water District. The district's local groundwater, its local surface water and the imported water it buys all rate very hard.
Why does my water seem harder some months?
Most providers blend groundwater with imported water and change the mix through the year. Irvine Ranch Water District's report says customers may notice a difference in hardness at different times of year, and that none of it affects safety. That is also why the ranges above are wide: they cover every source and every sample, not your tap on a given day.
What should I do about hard water at home?
Hard water leaves scale when it is heated, so the water heater comes first. Our step-by-step pages cover flushing a tank water heater and descaling a tankless one. What scale does to fixtures and appliances, and the California rules on water softeners, are in our hard water guide. If a heater is past saving, see the water heater replacement guide.
OakTend keeps the age of your water heater and reminds you when a flush or descale is due.
Track your water heater, freeFigures checked October 12, 2026, from each provider's report on 2025 sampling, linked under Sources. Providers publish a new report every year. General information, not plumbing or health advice.
Sources
- Anaheim Public Utilities: 2026 Water Quality Report
Checked 2026-10-02: groundwater 316 ppm (18 grains per gallon), Lenain plant 298 (17), Metropolitan 235 (14), range 162 to 431 ppm; groundwater served over 80 percent of customers in 2025. Re-checked 2026-10-12 on the identical copy filed with the State Water Resources Control Board, since the city site blocks automated reads. - City of Fountain Valley: 2026 Water Quality Report
Checked 2026-10-02: local groundwater 217 ppm, range 171 to 256, 13 grains per gallon; the city did not import water in 2025. - City of Garden Grove: 2026 Water Quality Report
Checked 2026-10-02: groundwater 303 ppm, range 187 to 346, 18 grains per gallon (range 11 to 20). - Golden State Water: Cowan Heights 2026 Annual Water Quality Report
Checked 2026-10-02: source water 236 mg/L, range 191 to 280, 13.8 grains per gallon; one grain per gallon equals 17.1 mg/L. - Golden State Water: Placentia-Yorba Linda 2026 Annual Water Quality Report
Checked 2026-10-02: source water 188 mg/L, range 67.1 to 299, 11.0 grains per gallon. - Golden State Water: West Orange County 2026 Annual Water Quality Report
Checked 2026-10-02: source water 237 mg/L, range 62.9 to 369, 13.8 grains per gallon. - City of Huntington Beach: Water Quality Report, reporting year 2025
Checked 2026-10-02: groundwater 162 ppm (10 grains per gallon), imported Metropolitan 236 (14), range 58.9 to 280; 85 percent groundwater and 15 percent imported in 2025. - Irvine Ranch Water District: 2026 Water Quality Report
Checked 2026-10-02: local groundwater 214 ppm (12.5 grains per gallon), local surface water 293 (17.1), imported Metropolitan 236 (13.8), range 52.0 to 469; hardness can differ at different times of year and does not affect safety. Re-checked 2026-10-12: IRWD serves all of Irvine, most of Lake Forest, and parts of Newport Beach, Tustin, Costa Mesa, Orange and unincorporated Orange County. - Mesa Water District: 2026 Consumer Confidence Report
Checked 2026-10-02: groundwater 113 ppm, range 20.6 to 293, 6.6 grains per gallon; 100 percent local groundwater. Re-checked 2026-10-12: serves most of Costa Mesa, a portion of Newport Beach and some unincorporated areas. - City of Newport Beach: 2026 Annual Water Quality Report
Checked 2026-10-02: groundwater 232 ppm, range 47.5 to 475, 14 grains per gallon; about 85 percent groundwater and 15 percent imported. - City of Orange: Consumer Confidence Report 2025, as filed with the State Water Resources Control Board
Checked 2026-10-02: hardness 300 ppm, range 130 to 380, 18 grains per gallon (range 8 to 22), 2025 sampling. - City of Santa Ana: 2025 Water Quality Tables
Checked 2026-10-02: groundwater 239 ppm, range 130 to 307, 14 grains per gallon; Metropolitan Diemer 236 and Weymouth 234 ppm. - City of Santa Ana: 2025 Consumer Confidence Report
Checked 2026-10-02: 85 percent groundwater and 15 percent imported water from Metropolitan; one grain per gallon equals 17.1 mg/L. - Santa Margarita Water District: 2026 Water Quality Report
Checked 2026-10-02: distribution system 256 ppm, range 210 to 300, 15 grains per gallon; supply is imported water from Metropolitan and IRWD's Baker plant. - City of Tustin: 2026 Annual Water Quality Report
Checked 2026-10-02: Tustin groundwater 377 ppm (22 grains per gallon), East Orange County Water District groundwater 333 (20), imported Metropolitan 236 (14), range 133 to 609. - Water Quality Association: glossary of terms, hardness
One grain per gallon equals 17.1 ppm as calcium carbonate; less than 1 grain per gallon is soft, 1 to 3.5 slightly hard, 3.5 to 7 moderately hard, 7 to 10.5 hard, and above 10.5 very hard. Checked 2026-10-09. - U.S. Geological Survey: Hardness of Water
Heated hard water forms calcium carbonate scale.