Last updated: November 8, 2026 · Data: City of San Diego Public Utilities Department water quality data via TapWaterData (CC BY 4.0)
Yes, San Diego has very hard water. City of San Diego Public Utilities Department reports total hardness of about 225 mg/L, or 13.2 grains per gallon (GPG), which is very hard on the U.S. Geological Survey scale. That ranks San Diego #7 for hardest water among the 86 large U.S. cities in our 2026 study, and above the California median of about 98 mg/L.
If you live in San Diego, you have probably seen the signs: white crust on faucets and shower heads, spotty dishes and soap that will not lather. This guide explains where San Diego’s water comes from, how hard it is compared with nearby cities and the rest of the country, and whether a water softener is worth it for your home.
San Diego water hardness at a glance
- Hardness: 225 mg/L (13.2 GPG)
- Category: Very hard
- Water utility: City of San Diego Public Utilities Department
- Data date: December 2024
- National rank: #7 hardest of 86 large U.S. cities
- Suggested softener hardness setting: about 15 GPG
Where Does San Diego Get Its Water?
Most of San Diego’s water is imported from the Colorado River and from Northern California through the State Water Project, supplemented by local reservoirs and, across the region, desalinated seawater. Colorado River water is especially hard, so the share of imported water in your supply has a big effect on hardness.
Hard water in San Diego shows up as white crust on shower heads, cloudy glassware and spots on cars, and it shortens the life of tankless water heaters if they are not descaled.
How Hard Is San Diego Water Compared With Other Places?
| Place | Hardness (mg/L) | GPG |
|---|---|---|
| San Diego, CA | 225 | 13.2 |
| California median | 98 | 5.8 |
| Median of 86 large U.S. cities | 112 | 6.5 |
| Hardest large city (Madison, WI) | 341 | 19.9 |
| Softest large city (Boston, MA) | 17 | 1.0 |
See the full rankings in our study of cities with the hardest water in the USA, or compare states on our US hard water map.
Water Hardness in Cities Near San Diego
| City | Hardness (mg/L) | GPG | Category | Distance |
|---|---|---|---|---|
| Coronado | 160 | 9.4 | Hard | 3 mi |
| National City | 128 | 7.5 | Hard | 5 mi |
| Chula Vista | 216 | 12.6 | Very hard | 7 mi |
| Lemon Grove | 150 | 8.8 | Hard | 7 mi |
| Bonita | 216 | 12.6 | Very hard | 9 mi |
| La Mesa | 150 | 8.8 | Hard | 9 mi |
| Spring Valley | 189 | 11.1 | Very hard | 9 mi |
| Imperial Beach | 200 | 11.7 | Very hard | 10 mi |
Nearby cities can have very different water because they use different utilities, wells or treatment plants.
What 13.2 GPG Hard Water Means for Your Home
- Scale: white, chalky buildup on faucets, shower heads, glass doors and inside kettles.
- Water heater: scale settles in the tank and on heating elements, lowering efficiency and shortening its life.
- Dishes and laundry: spots and film on glasses, stiff towels and faded colors.
- Skin and hair: soap scum can leave skin feeling dry and hair dull.
- Cleaning: you need more soap and detergent. See how to remove hard water stains.
Do You Need a Water Softener in San Diego?
At 13.2 grains per gallon, most San Diego homes will notice a big difference with a water softener. Here is a quick sizing example for a family of four using about 300 gallons a day:
- Daily hardness load: 300 gallons × 13.2 GPG = about 3,960 grains a day
- Weekly load: about 28,000 grains
- Suggested softener size: 32,000 to 40,000 grains
- Hardness setting: about 15 GPG (your hardness plus a small buffer)
- Sodium added: about 25 mg per 8-ounce glass of softened water
Learn more in how a water softener works, what size softener you need and water softener cost. If you would rather avoid salt, compare salt-free conditioners, which reduce scale but do not remove hardness.
Is San Diego Tap Water Safe to Drink?
Hard water is not a health risk, and the EPA sets no health limit for hardness. City of San Diego Public Utilities Department is required to meet EPA drinking water standards and publishes an annual water quality report (Consumer Confidence Report) with its test results. If you have your own test results, compare them with EPA limits using our water test results checker.
Check the Hardness at Your Address
Hardness can vary by neighborhood. Enter your ZIP code below to see the data for your area.
Data: TapWaterData US Water Hardness Dataset (CC BY 4.0), based on utility water quality reports. ZIP locations: GeoNames (CC BY 4.0).
Frequently Asked Questions
Does San Diego have hard water?
Yes. San Diego’s water is very hard, at about 225 mg/L (13.2 grains per gallon) according to City of San Diego Public Utilities Department.
How hard is San Diego water in grains per gallon?
About 13.2 grains per gallon (GPG), or 225 mg/L as calcium carbonate. Anything above 7 GPG is considered hard, and above 10.5 GPG is very hard.
What should I set my water softener to in San Diego?
Start with about 15 GPG, which is San Diego’s hardness plus a small buffer. If your home has iron in the water, add about 4 GPG for each 1 mg/L of iron. Test your softened water to confirm it reads close to zero.
Where does San Diego get its drinking water?
Most of San Diego’s water is imported from the Colorado River and from Northern California through the State Water Project, supplemented by local reservoirs and, across the region, desalinated seawater.
Is San Diego hard water bad for you?
No. Hard water is not considered a health risk. It mainly causes scale, spotty dishes, poor soap lather and dry skin, which a water softener fixes.
Sources: City of San Diego Public Utilities Department annual water quality report, via TapWaterData US Water Hardness Dataset (CC BY 4.0); USGS: Hardness of Water.