{
  "city": "San Diego",
  "state": "CA",
  "slug": "san-diego",
  "hardness_facts": [
    {
      "utility": "City of San Diego Public Utilities",
      "measure": "Total hardness, Alvarado plant",
      "value_as_published": "Average 237 ppm (13.8 grains per gallon), range 203-270 ppm",
      "period": "Calendar year 2025",
      "source_title": "Annual Drinking Water Quality Report (2025 data)",
      "source_url": "https://www.sandiego.gov/sites/default/files/2026-06/pud-annual-drinking-water-quality-report-2025.pdf"
    },
    {
      "utility": "City of San Diego Public Utilities",
      "measure": "Total hardness, Miramar plant",
      "value_as_published": "Average 242 ppm (14.1 grains per gallon), range 200-285 ppm",
      "period": "Calendar year 2025",
      "source_title": "Annual Drinking Water Quality Report (2025 data)",
      "source_url": "https://www.sandiego.gov/sites/default/files/2026-06/pud-annual-drinking-water-quality-report-2025.pdf"
    },
    {
      "utility": "City of San Diego Public Utilities",
      "measure": "Total hardness, Otay plant",
      "value_as_published": "Average 243 ppm (14.2 grains per gallon), range 201-271 ppm",
      "period": "Calendar year 2025",
      "source_title": "Annual Drinking Water Quality Report (2025 data)",
      "source_url": "https://www.sandiego.gov/sites/default/files/2026-06/pud-annual-drinking-water-quality-report-2025.pdf"
    },
    {
      "utility": "City of San Diego Public Utilities",
      "measure": "Total hardness, purchased treated water",
      "value_as_published": "Average 145 ppm (8.5 grains per gallon), range 54.4-232 ppm",
      "period": "Calendar year 2025",
      "source_title": "Annual Drinking Water Quality Report (2025 data)",
      "source_url": "https://www.sandiego.gov/sites/default/files/2026-06/pud-annual-drinking-water-quality-report-2025.pdf"
    }
  ],
  "published_span_mg_per_l": [
    54.4,
    285
  ],
  "span_converted_from_grains": false,
  "usgs_class": "soft to very hard",
  "usgs_class_source": "https://www.usgs.gov/water-science-school/science/hardness-water",
  "notes": [
    "Most of the supply is imported from the Colorado River and the State Water Project."
  ],
  "local_details": {
    "disinfectant": {
      "text": "San Diego uses chloramine to keep water disinfected in the pipes, after ozone or chlorine dioxide treatment at its plants.",
      "kind": "chloramine",
      "source_title": "City of San Diego 2025 Annual Drinking Water Quality Report",
      "source_url": "https://www.sandiego.gov/sites/default/files/2026-06/pud-annual-drinking-water-quality-report-2025.pdf",
      "evidence_ids": [
        "SANDIE-L-01"
      ]
    },
    "source_water": {
      "text": "Most San Diego water is imported through the County Water Authority, mainly a Colorado River and State Water Project blend, with local reservoir water, treated at the Alvarado, Miramar and Otay plants.",
      "source_title": "City of San Diego 2025 Annual Drinking Water Quality Report",
      "source_url": "https://www.sandiego.gov/sites/default/files/2026-06/pud-annual-drinking-water-quality-report-2025.pdf",
      "evidence_ids": [
        "SANDIE-L-02"
      ]
    },
    "seasonal": {
      "text": "The city says the share of water from each source changes through the year.",
      "source_title": "City of San Diego 2025 Annual Drinking Water Quality Report",
      "source_url": "https://www.sandiego.gov/sites/default/files/2026-06/pud-annual-drinking-water-quality-report-2025.pdf",
      "evidence_ids": [
        "SANDIE-L-03"
      ]
    }
  },
  "sources_checked_on": "2026-10-27",
  "site": "https://sandiegowatersystems.com/",
  "brand": "San Diego Water Systems by My Home Water System",
  "taking_requests": true
}