Water hardness in Sonoma
3.2 gpg soft
Tap water in Sonoma is soft: 3.2 gpg (56 mg/L · 3.1 °dH · 5.5 °fH).
Source: California SWRCB Division of Drinking Water, EDT lab results, system CA4910012 (2026-01) · data checked 2026-10-19
Range across supply zones: 35–65 mg/L.
The Sonoma figure comes from State Water Resources Control Board lab results for the City of Sonoma system. The median of 10 results from 2021 to 2026, taken at 5 well points, is 55.5 mg/L as CaCO3 (3.2 gpg), with a range of 35 to 65.3 mg/L. This is soft water. Scale is minor, and a softener adds little for hardness.
USGS classes: soft 0–60, moderately hard 61–120, hard 121–180, very hard >180 mg/L.
Water data
| Total hardness | 3.2 gpg |
|---|---|
| Utility | Sonoma, City Of |
How Sonoma compares
- Tap water in Sonoma is 64 % softer than the median of the 1372 cities we track in the United States (9.1 gpg).
- By hardness it ranks 1197 of 1372 in the United States (1 = hardest); 13 % of these cities have softer water.
- In California it is number 298 of 336 cities; the regional median is 9.5 gpg.
- Nearest city with clearly softer water: Berkeley, 49 km away (1.6 gpg).
- Nearest city with clearly harder water: Napa, 14 km away (4.4 gpg).
Ranking of the hardest and softest water in the United States →
What it means at home
- Little or no limescale in kettles, water heaters or washing machines.
- Soap lathers easily; water does not dry skin or hair.
- Dishwasher: salt setting at minimum or off.
- No softener needed; a jug filter only changes taste.
How much salt will you use for softening?
No. Water this soft does not need softening.
Descale a coffee machine or kettle about every 6 months (typical manufacturer guidance for this hardness).
Estimates for planning, not a quote. Check your appliance manual for exact settings.
Dishwasher setting in Sonoma
| Brand | Setting for this water |
|---|---|
| Bosch | H00 |
| Miele | 3 °dH |
| AEG / Electrolux | 1 |
| Beko | 1st |
| Hoover | S0 |
| LG | H0 |
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 Sonoma water hard or soft?
It is soft: 56 mg/L as CaCO₃ (3.2 gpg, 3.1 °dH). The usual bands are soft < 60, moderately hard 60–120, hard 120–180 and very hard > 180 mg/L.
Is tap water in Sonoma 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 Sonoma water?
3.2 gpg, equal to 3.1 °dH, 5.5 °fH or 56 mg/L calcium carbonate.
What dishwasher salt setting should I use in Sonoma?
For 56 mg/L (3.1 °dH) check your manufacturer's table: level 0–1, usually no salt.
Do I need a water softener in Sonoma?
No. With soft water a softener adds nothing.
Source
Source: California SWRCB Division of Drinking Water, EDT lab results, system CA4910012 (2026-01). Method: own measurement. California SWRCB Division of Drinking Water, EDT lab results, system CA4910012 · Outdated figure? Tell us