# San Diego Water Systems by My Home Water System

> Published water hardness for San Diego, CA, copied from the utility's own reports, and a way to request a written water treatment quote from one local company. Not a water utility.

## Water facts, as published
- Total hardness, Alvarado plant, City of San Diego Public Utilities: Average 237 ppm (13.8 grains per gallon), range 203-270 ppm (Calendar year 2025). Source: Annual Drinking Water Quality Report (2025 data), https://www.sandiego.gov/sites/default/files/2026-06/pud-annual-drinking-water-quality-report-2025.pdf
- Total hardness, Miramar plant, City of San Diego Public Utilities: Average 242 ppm (14.1 grains per gallon), range 200-285 ppm (Calendar year 2025). Source: Annual Drinking Water Quality Report (2025 data), https://www.sandiego.gov/sites/default/files/2026-06/pud-annual-drinking-water-quality-report-2025.pdf
- Total hardness, Otay plant, City of San Diego Public Utilities: Average 243 ppm (14.2 grains per gallon), range 201-271 ppm (Calendar year 2025). Source: Annual Drinking Water Quality Report (2025 data), https://www.sandiego.gov/sites/default/files/2026-06/pud-annual-drinking-water-quality-report-2025.pdf
- Total hardness, purchased treated water, City of San Diego Public Utilities: Average 145 ppm (8.5 grains per gallon), range 54.4-232 ppm (Calendar year 2025). Source: Annual Drinking Water Quality Report (2025 data), https://www.sandiego.gov/sites/default/files/2026-06/pud-annual-drinking-water-quality-report-2025.pdf
- USGS class, our reading of the published figures: soft to very hard. Classes: https://www.usgs.gov/water-science-school/science/hardness-water
- Most of the supply is imported from the Colorado River and the State Water Project.
- San Diego uses chloramine to keep water disinfected in the pipes, after ozone or chlorine dioxide treatment at its plants. Source: City of San Diego 2025 Annual Drinking Water Quality Report, https://www.sandiego.gov/sites/default/files/2026-06/pud-annual-drinking-water-quality-report-2025.pdf
- 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: City of San Diego 2025 Annual Drinking Water Quality Report, https://www.sandiego.gov/sites/default/files/2026-06/pud-annual-drinking-water-quality-report-2025.pdf
- The city says the share of water from each source changes through the year. Source: City of San Diego 2025 Annual Drinking Water Quality Report, https://www.sandiego.gov/sites/default/files/2026-06/pud-annual-drinking-water-quality-report-2025.pdf
- Sources last checked: 2026-10-27

## Pages
- [San Diego water and quotes](https://sandiegowatersystems.com/): the answer, the sources, common questions
- [Water data as JSON](https://sandiegowatersystems.com/water.json)
- [San Diego water by treatment plant](https://sandiegowatersystems.com/by-area/): where each area or utility serves, its own figures and treatment
- [Water softeners](https://www.myhomewatersystem.com/water-softeners/), [whole-home filtration](https://www.myhomewatersystem.com/whole-home-filtration/), [reverse osmosis](https://www.myhomewatersystem.com/reverse-osmosis/)
- [Hard water by city](https://www.myhomewatersystem.com/hard-water-by-city/): published hardness for every city we cover

## Status
- Taking requests. No prices are published; quotes come after an assessment at the home.
- Run by My Home Water System, operated by Aidren LLC.