Tap water report · updated November 2026
San Diego tap water: very hard water, lithium up to 65 µg/L
What’s in the water City of San Diego Public Utilities delivers to 1.4 million people, from national testing by the U.S. Environmental Protection Agency (EPA) and the utility’s own report.
Short answer
San Diego tap water is very hard: about 14.0 grains per gallon (240 milligrams per liter (mg/L)), depending on which treatment plant serves your neighborhood (145 to 243 mg/L), according to published water quality data from City of San Diego Public Utilities (2025). The U.S. Environmental Protection Agency’s (EPA’s) 2023 testing found no PFOA or PFOS (two PFAS “forever chemicals”) at or above its 4 parts per trillion (ppt) limit. Lithium reached 65 micrograms per liter (µg/L), above EPA’s 10 µg/L health reference level, which is not a legal limit. The system had no health-based violations in the five years through September 2026. Of the 40 large US water systems The Water Monitor tracks, San Diego has the 5th-hardest water.
Sources: City of San Diego Public Utilities 2025 data, EPA UCMR 5, EPA SDWIS 2026Q3 · Sources and method
How San Diego compares with the 40 systems we track
Hardness
5th hardest
of 34 systems
PFOA / PFOS
Not detected
in any EPA sample
Lithium
6th highest
of 14 that detected it
Size
11th largest
of 40 by people served
01 · What it means
What these readings mean for your home
Each reading in plain English: what it is, how San Diego compares with the other systems we track, and whether there’s anything to do. The tags follow EPA’s limits and reference levels where EPA has one; for hardness, which has no EPA limit, they follow the U.S. Geological Survey (USGS) scale and Minnesota’s health department. New to the acronyms? Every term, in plain English.
Hardness
Worth acting onHardness is dissolved calcium and magnesium, picked up as water runs through rock. It isn’t a health issue (EPA has no limit for it). It’s what leaves white crust on faucets, spots on glasses and scale inside your water heater. It’s measured in grains per gallon (gpg); 1 gpg is about 17 mg of minerals in a liter.
Here: At 14.0 gpg, San Diego water is very hard, the 5th-hardest of the 34 systems we track. You’ll see scale on fixtures and inside appliances.
What to do: A water softener is the only whole-house system that removes hardness. Size it to your household so it doesn’t waste salt.
What the research says: Studies tie hard water to more soap use and scale. Observational studies link it with somewhat more eczema in babies, but in the largest trial a softener didn’t improve existing eczema. The studies →
Learn more →PFAS (PFOA and PFOS)
Nothing to doPFAS are a family of thousands of manufactured chemicals used in many consumer and industrial products. They break down very slowly, which is why people call them "forever chemicals." PFOA and PFOS are the two EPA regulates most tightly. They’re measured in parts per trillion (ppt): 1 ppt is about one drop in 20 Olympic swimming pools.
Here: EPA’s 2023 testing found no PFOA or PFOS in San Diego’s water at or above 4 ppt, the lowest level labs can reliably measure. 29 of the 40 systems we track can say the same; 11 had a sample over the limit.
What to do: Nothing needed by EPA’s standard. If you want PFAS lower still, the same certified filters apply.
What the research says: EPA and the National Academies link PFOA and PFOS exposure to higher cholesterol, lower vaccine response, lower birth weight and some cancers, mostly over years of drinking the water. The studies →
Learn more →Disinfectant
Nothing to doUtilities add a small amount of chlorine, or chloramine (chlorine combined with a little ammonia), so germs can’t grow in the pipes on the way to your tap. EPA allows up to 4 milligrams per liter (mg/L) of either and says water within its standards can be used for drinking, cooking and bathing.
Here: San Diego uses chloramine, like 20 other systems we track. It lasts longer in pipes than chlorine and is harder to filter.
What to do: For taste, use catalytic carbon or a filter certified to NSF/ANSI 42 for chloramine. Fish tanks and home dialysis need it removed completely.
What the research says: Health agencies call these levels acceptable for drinking and bathing; dialysis and fish tanks are the exceptions. Studies haven’t shown shower chlorine harms skin or hair. The studies →
Learn more →Lithium
Worth knowingLithium is a metal that occurs naturally in some rock and groundwater. There’s no legal limit in drinking water. EPA screens results against 10 micrograms per liter (µg/L) while it studies whether a limit is needed.
Here: San Diego’s highest sample was 65 µg/L, about 7 times EPA’s screening level, 6th-highest of the 40. 11 of the 40 were above it. Nationally, about 24% of large systems are.
What to do: No action is required, since there’s no limit. If you want less, ask a filter maker for independent test data on lithium specifically, since a PFAS or chlorine certification says nothing about it.
What the research says: Some regional studies link natural lithium with lower suicide rates and the largest individual study found no link. EPA’s screening level is cautious, not a harm threshold. The studies →
Learn more →Health-based violations
Nothing to doA health-based violation means the utility broke a federal drinking water rule tied to health: it went over a limit, or skipped a required treatment step. Missing a paperwork deadline doesn’t count.
Here: San Diego’s system had none in the five years through September 2026. That’s normal for a large system: 36 of the 40 we track had none.
What to do: Nothing to do.
Learn more →How San Diego compares: highest PFOA or PFOS sample
Parts per trillion (ppt), from EPA’s 2023–25 testing. The dashed line is EPA’s limit of 4.
San Diego: none at or above 4 ppt. Like 28 other systems we track, EPA’s testing found no PFOA or PFOS there. These 11 did:
- Miami33.0 PFOS
- El Paso8.5 PFOS
- Fort Worth8.3 PFOA
- Philadelphia8.1 PFOA
- Louisville7.5 PFOA
- Tampa6.9 PFOS
- Dallas6.3 PFOA
- San Jose6.2 PFOS
- Cincinnati6.1 PFOS
- Columbus5.3 PFOA
- Austin4.8 PFOS
If you live in San Diego
- Size a softener for San Diego water At 14.0 grains per gallon, the calculator works out the capacity for your household.
- What softeners cost Store and dealer prices, with what each includes.
- Whole-house filters for chloramine San Diego uses chloramine, which ordinary carbon removes slowly. What to look for and what it costs.
San Diego’s water is very hard. Softeners from brands that sell online, at their own store prices:
We may earn a commission from these links.
02 · The full results
Every PFAS result EPA recorded
EPA’s national testing (sampled 2023) found no PFOA or PFOS at or above 4 ppt in any of 16 samples, which puts San Diego under EPA’s limit for both.
Lithium reached 65 µg/L, above EPA’s health reference level of 10 µg/L. That level is a screening benchmark, not a legal limit, and about 24% of large US systems tested above it.
Results from EPA’s national testing program (UCMR 5) for City of San Diego Public Utilities, 4 sampling points, January 2023 to December 2023. Concentrations in parts per trillion (ppt).
| Chemical | Samples | Detected | Highest | EPA limit |
|---|---|---|---|---|
| PFOA (perfluorooctanoic acid) | 16 | 0 | none | 4 |
| PFOS (perfluorooctane sulfonic acid) | 16 | 0 | none | 4 |
| PFHxS | 16 | 0 | none | 10 |
| PFNA | 16 | 0 | none | 10 |
| HFPO-DA (GenX) | 16 | 0 | none | 10 |
"None" means every sample was under EPA’s reporting level (4 ppt for PFOA). PFHxS, PFNA and HFPO-DA (GenX) are three other PFAS chemicals; EPA proposed removing their limits in May 2026, and that isn’t final.
03 · Where it comes from
The source, and who else drinks it
San Diego imports most of its supply as raw water from the San Diego County Water Authority, mostly a blend of Colorado River and State Water Project water, treats it at the Alvarado, Miramar and Otay plants, and buys a small amount of treated water from MWD’s Skinner plant, the Water Authority’s Twin Oaks plant and the Carlsbad Desalination Plant.
City of San Diego Public Utilities serves about 1.4 million people directly, and 9 other water systems buy water from it, serving about 853,577 more. If you live in one of them, most of what’s on this page describes your water too, though hardness and disinfectant can change if your system blends in its own wells.
Construction on Phase 1 of the Pure Water San Diego purification project was 90 percent complete when the 2025 report was published.
San Diego’s water system had no health-based violations in the five years through September 2026, according to EPA’s federal database.
Largest systems that buy from City of San Diego Public Utilities
- Helix Water District277,918
- Otay Water District242,155
- Sweetwater Authority184,915
- Cal-am Water Coronado106,000
- Fallbrook PUD35,237
- Del Mar, City of3,950
- Naval Medical Center San Diego2,981
- Nas North Island & Nab Coronado421
- San Diego County Water Authority0
From EPA’s federal drinking water database (SDWIS), 2026Q3: community systems with an active connection buying from CA3710020. Population served.
ZIP codes City of San Diego Public Utilities reports serving (63)
91902 · 91910 · 91911 · 91913 · 91915 · 91932 · 91941 · 91942 · 91945 · 91950 · 91977 · 92008 · 92014 · 92019 · 92020 · 92021 · 92025 · 92027 · 92037 · 92040 · 92064 · 92065 · 92067 · 92071 · 92075 · 92093 · 92101 · 92102 · 92103 · 92104 · 92105 · 92106 · 92107 · 92108 · 92109 · 92110 · 92111 · 92113 · 92114 · 92115 · 92116 · 92117 · 92119 · 92120 · 92121 · 92122 · 92123 · 92124 · 92126 · 92127 · 92128 · 92129 · 92130 · 92131 · 92134 · 92136 · 92139 · 92140 · 92145 · 92154 · 92161 · 92173 · 92182
From EPA’s UCMR 5 ZIP file. A ZIP can be served by more than one system; your water bill names yours. Look up any ZIP.
04 · Questions
San Diego water questions
Is San Diego tap water safe to drink?
The U.S. Environmental Protection Agency (EPA) doesn’t grade a city’s tap water as safe or unsafe; it sets limits and records violations. By that record, San Diego’s water system had no health-based violations of federal drinking water rules in the five years through September 2026. EPA’s 2023 testing found no PFOA or PFOS (two PFAS “forever chemicals”) samples above its 4 parts per trillion (ppt) limit.
Is San Diego tap water hard?
San Diego tap water is very hard: about 14.0 grains per gallon (240 milligrams per liter (mg/L)), depending on which treatment plant serves your neighborhood (145 to 243 mg/L), according to published water quality data from City of San Diego Public Utilities (2025).
Does San Diego tap water have PFAS?
The U.S. Environmental Protection Agency’s (EPA’s) national testing (sampled 2023) found no PFOA or PFOS (two PFAS “forever chemicals”) at or above 4 parts per trillion (ppt) in any of 16 samples, which puts San Diego under EPA’s limit for both.
Does San Diego use chlorine or chloramine?
Chloramine. The Alvarado and Miramar treatment plants use ozone and the Otay plant uses chlorine dioxide as the primary disinfectant, and the City uses chloramines as the residual disinfectant in the distribution system, which averaged 1.75 parts per million (ppm) in 2025.
Has San Diego’s water system had violations?
San Diego’s water system had no health-based violations in the five years through September 2026, according to the U.S. Environmental Protection Agency’s (EPA’s) federal database.
Is there lithium in San Diego water?
Lithium reached 65 micrograms per liter (µg/L), above the U.S. Environmental Protection Agency’s (EPA’s) health reference level of 10 µg/L. That level is a screening benchmark, not a legal limit, and about 24% of large US systems tested above it.
Nearest cities we cover
Sources
- 01City of San Diego Public Utilities, 2025 water quality data (hardness), read 2026-11-04
- 02City of San Diego Public Utilities (source water)
- 03City of San Diego Public Utilities (disinfectant)
- 04EPA, Fifth Unregulated Contaminant Monitoring Rule (UCMR 5) occurrence data, file posted 2026-10-15
- 05EPA, Safe Drinking Water Information System via ECHO, 2026Q3 file
- 06EPA, PFAS National Primary Drinking Water Regulation, 89 FR 32532
- 07EPA UCMR 5 Data Summary (July 2026)
- 08USGS Water Science School, "Hardness of Water"
EPA system ID CA3710020 · City of San Diego Public Utilities