Water hardness in Tustin
17.9 gpg very hard
Tap water in Tustin is very hard: 17.9 gpg (307 mg/L · 17.2 °dH · 30.7 °fH).
Source: California SWRCB Division of Drinking Water, EDT lab results, system CA3010046 (2026-04) · data checked 2026-10-19
Range across supply zones: 135–609 mg/L.
The Tustin figure comes from State Water Resources Control Board lab results for the City of Tustin system. The median of 41 results from 2022 to 2026, taken at wells and treatment plants together, is 307 mg/L as CaCO3 (17.9 gpg), with a range of 135 to 609 mg/L. Treatment-plant samples alone read lower, so confidence in the exact figure is moderate. The water is very hard overall.
USGS classes: soft 0–60, moderately hard 61–120, hard 121–180, very hard >180 mg/L.
Water data
| Total hardness | 17.9 gpg |
|---|---|
| Utility | City Of Tustin |
How Tustin compares
- Tap water in Tustin is 98 % harder than the median of the 1372 cities we track in the United States (9.1 gpg).
- By hardness it ranks 239 of 1372 in the United States (1 = hardest); 82 % of these cities have softer water.
- In California it is number 44 of 336 cities; the regional median is 9.5 gpg.
- Nearest city with clearly softer water: Irvine, 7 km away (8.6 gpg).
- Nearest city with clearly harder water: Torrance, 52 km away (26.8 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 Tustin
| Brand | Setting for this water |
|---|---|
| Bosch | H05 |
| Miele | 17 °dH |
| AEG / Electrolux | 4 |
| Beko | 5th |
| Hoover | S3 |
| LG | H3 |
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 Tustin water hard or soft?
It is very hard: 307 mg/L as CaCO₃ (17.9 gpg, 17.2 °dH). The usual bands are soft < 60, moderately hard 60–120, hard 120–180 and very hard > 180 mg/L.
Is tap water in Tustin 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 Tustin water?
17.9 gpg, equal to 17.2 °dH, 30.7 °fH or 307 mg/L calcium carbonate.
What dishwasher salt setting should I use in Tustin?
For 307 mg/L (17.2 °dH) check your manufacturer's table: maximum level (5–7).
Do I need a water softener in Tustin?
Yes, unless you are only passing through: scale damages appliances within a few years.
Source
Source: California SWRCB Division of Drinking Water, EDT lab results, system CA3010046 (2026-04). Method: own measurement. California SWRCB Division of Drinking Water, EDT lab results, system CA3010046 · Outdated figure? Tell us