{
  "city": "San Francisco",
  "state": "CA",
  "slug": "san-francisco",
  "hardness_facts": [
    {
      "utility": "SFPUC",
      "measure": "Hardness",
      "value_as_published": "Average 62 ppm, range 8.1-112 ppm",
      "period": "Calendar year 2025",
      "source_title": "2025 Annual Water Quality Report (City of San Francisco)",
      "source_url": "https://www.sfpuc.gov/vi/sites/default/files/accounts-and-services/water-quality/water-quality-en-SF-2025.pdf"
    }
  ],
  "published_span_mg_per_l": [
    8.1,
    112
  ],
  "span_converted_from_grains": false,
  "usgs_class": "soft to moderately hard",
  "usgs_class_source": "https://www.usgs.gov/water-science-school/science/hardness-water",
  "notes": [],
  "local_details": {
    "disinfectant": {
      "text": "SFPUC disinfects with ultraviolet light and chlorine and keeps the water disinfected in the pipes with chloramine.",
      "kind": "chloramine",
      "source_title": "SFPUC 2025 Water Quality Report",
      "source_url": "https://www.sfpuc.gov/vi/sites/default/files/accounts-and-services/water-quality/water-quality-en-SF-2025.pdf",
      "evidence_ids": [
        "SANFRA-L-01"
      ]
    },
    "source_water": {
      "text": "Hetch Hetchy Reservoir supplies up to 85 percent of San Francisco water each year, with the rest from Bay Area reservoirs and a small amount of local groundwater.",
      "source_title": "SFPUC 2025 Water Quality Report",
      "source_url": "https://www.sfpuc.gov/vi/sites/default/files/accounts-and-services/water-quality/water-quality-en-SF-2025.pdf",
      "evidence_ids": [
        "SANFRA-L-02"
      ]
    },
    "seasonal": {
      "text": "SFPUC says blending different sources through the year gave varying water quality.",
      "source_title": "SFPUC 2025 Water Quality Report",
      "source_url": "https://www.sfpuc.gov/vi/sites/default/files/accounts-and-services/water-quality/water-quality-en-SF-2025.pdf",
      "evidence_ids": [
        "SANFRA-L-03"
      ]
    }
  },
  "sources_checked_on": "2026-10-27",
  "site": "https://sanfranciscowatersystems.com/",
  "brand": "San Francisco Water Systems by My Home Water System",
  "taking_requests": false
}