Water hardness in San Diego
14 gpg very hard
Tap water in San Diego is very hard: 14 gpg (240 mg/L · 13.4 °dH · 23.9 °fH).
Source: City of San Diego 2025 Annual Drinking Water Quality Report (2025) · data checked 2026-10-19
Range across supply zones: 54–285 mg/L.
4 supply zones — hardness varies by neighbourhood; the figure above is the median.
Hardness by district / supply zone
| gpg | mg/L | ||
|---|---|---|---|
| Alvarado WTP | 13.8 | 237 | very hard |
| Miramar WTP | 14.1 | 242 | very hard |
| Otay WTP | 14.2 | 243 | very hard |
| Purchased treated water (imported) | 8.5 | 145 | hard |
The City of San Diego reports three of its own treatment plants (Alvarado, Miramar and Otay) at averages of 237 to 243 mg/L. It also sells purchased treated water that is softer, averaging 145 mg/L, so the blend varies by area. The page shows 239.5 mg/L (14.0 gpg), with a full range of 54.4 to 285 mg/L. In most of the city, expect heavy scale on heaters and fixtures.
USGS classes: soft 0–60, moderately hard 61–120, hard 121–180, very hard >180 mg/L.
Water data
| Total hardness | 14 gpg |
|---|---|
| Utility | City of San Diego Public Utilities Department |
How San Diego compares
- Tap water in San Diego is 54 % harder than the median of the 1372 cities we track in the United States (9.1 gpg).
- By hardness it ranks 408 of 1372 in the United States (1 = hardest); 70 % of these cities have softer water.
- In California it is number 82 of 336 cities; the regional median is 9.5 gpg.
- Nearest city with clearly softer water: Temecula, 86 km away (11.1 gpg).
- Nearest city with clearly harder water: Hemet, 114 km away (18.1 gpg).
Ranking of the hardest and softest water in the United States →
What it means at home
- Severe scale: heater elements and washing-machine heaters fail early.
- Detergent use is very high; taps and screens coat within days.
- Dishwasher at maximum salt setting.
- An ion-exchange softener is practically essential; RO for drinking water.
How much salt will you use for softening?
Yes. At this hardness a softener pays for itself through appliance life and detergent.
Descale a coffee machine or kettle about every 1 months (typical manufacturer guidance for this hardness).
Estimates for planning, not a quote. Check your appliance manual for exact settings.
Dishwasher setting in San Diego
| Brand | Setting for this water |
|---|---|
| Bosch | H04 |
| Miele | 13 °dH |
| AEG / Electrolux | 3 |
| Beko | 4th |
| Hoover | S2 |
| LG | H2 |
From each brand's manual for the model family named in the source; your model may differ, so check its manual. All brands and how to change the setting →
FAQ
Is San Diego water hard or soft?
It is very hard: 240 mg/L as CaCO₃ (14 gpg, 13.4 °dH). The usual bands are soft < 60, moderately hard 60–120, hard 120–180 and very hard > 180 mg/L.
Is tap water in San Diego safe to drink?
Hardness is not a health issue; it is about limescale, taste and appliances. Mains water must meet national drinking-water standards. USGS classes: soft 0–60, moderately hard 61–120, hard 121–180, very hard >180 mg/L.
How many grains per gallon is San Diego water?
14 gpg, equal to 13.4 °dH, 23.9 °fH or 240 mg/L calcium carbonate.
What dishwasher salt setting should I use in San Diego?
For 240 mg/L (13.4 °dH) check your manufacturer's table: maximum level (5–7).
Do I need a water softener in San Diego?
Yes, unless you are only passing through: scale damages appliances within a few years.
Source
Source: City of San Diego 2025 Annual Drinking Water Quality Report (2025). Method: figure published by the water supplier. City of San Diego 2025 Annual Drinking Water Quality Report · Outdated figure? Tell us