Water hardness in Fairfield
10.7 gpg very hard
Tap water in Fairfield is very hard: 10.7 gpg (183 mg/L · 10.3 °dH · 18.3 °fH).
Source: California SWRCB Division of Drinking Water, EDT lab results, system CA4810003 (2026-04) · data checked 2026-10-19
Range across supply zones: 134–199 mg/L.
The Fairfield figure comes from State Water Resources Control Board lab results for the City of Fairfield system, using finished-water samples from two treatment-plant points. The median of 44 results from 2021 to 2026 is 183 mg/L as CaCO3 (10.7 gpg), with a range of 134.3 to 198.7 mg/L. That is just over the line into very hard. Scale builds steadily on heaters and glassware.
USGS classes: soft 0–60, moderately hard 61–120, hard 121–180, very hard >180 mg/L.
Water data
| Total hardness | 10.7 gpg |
|---|---|
| Utility | City Of Fairfield |
How Fairfield compares
- Tap water in Fairfield is 18 % harder than the median of the 1372 cities we track in the United States (9.1 gpg).
- By hardness it ranks 585 of 1372 in the United States (1 = hardest); 57 % of these cities have softer water.
- In California it is number 143 of 336 cities; the regional median is 9.5 gpg.
- Nearest city with clearly softer water: Benicia, 24 km away (4.9 gpg).
- Nearest city with clearly harder water: Davis, 42 km away (26.3 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 Fairfield
| Brand | Setting for this water |
|---|---|
| Bosch | H02 |
| Miele | 10 °dH |
| AEG / Electrolux | 2 |
| Beko | 3rd |
| 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 Fairfield water hard or soft?
It is very hard: 183 mg/L as CaCO₃ (10.7 gpg, 10.3 °dH). The usual bands are soft < 60, moderately hard 60–120, hard 120–180 and very hard > 180 mg/L.
Is tap water in Fairfield 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 Fairfield water?
10.7 gpg, equal to 10.3 °dH, 18.3 °fH or 183 mg/L calcium carbonate.
What dishwasher salt setting should I use in Fairfield?
For 183 mg/L (10.3 °dH) check your manufacturer's table: maximum level (5–7).
Do I need a water softener in Fairfield?
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 CA4810003 (2026-04). Method: own measurement. California SWRCB Division of Drinking Water, EDT lab results, system CA4810003 · Outdated figure? Tell us