Water hardness in Rio Vista
3.9 gpg moderately hard
Tap water in Rio Vista is moderately hard: 3.9 gpg (67 mg/L · 3.8 °dH · 6.7 °fH).
Source: California SWRCB Division of Drinking Water, EDT lab results, system CA4810004 (2026-03) · data checked 2026-10-19
Range across supply zones: 42–84 mg/L.
The Rio Vista figure comes from State Water Resources Control Board lab results for the City of Rio Vista system. The median of 27 results from 2021 to 2026, taken at 7 well points, is 67 mg/L as CaCO3 (3.9 gpg), with a range of 42 to 84.4 mg/L. That is moderately hard water, close to the soft line. Scale builds slowly.
USGS classes: soft 0–60, moderately hard 61–120, hard 121–180, very hard >180 mg/L.
Water data
| Total hardness | 3.9 gpg |
|---|---|
| Utility | City Of Rio Vista |
How Rio Vista compares
- Tap water in Rio Vista is 57 % softer than the median of the 1372 cities we track in the United States (9.1 gpg).
- By hardness it ranks 1155 of 1372 in the United States (1 = hardest); 16 % of these cities have softer water.
- In California it is number 284 of 336 cities; the regional median is 9.5 gpg.
- Nearest city with clearly softer water: Isleton, 9 km away (0.9 gpg).
- Nearest city with clearly harder water: Pittsburg, 25 km away (7.1 gpg).
Ranking of the hardest and softest water in the United States →
What it means at home
- Visible kettle scale every few weeks; vinegar or citric acid is enough.
- Water heater and washing machine: some long-term scale; a scale inhibitor slows it.
- Dishwasher: medium salt setting.
- Softener optional; pays off mainly with a gas boiler or tankless heater.
How much salt will you use for softening?
Optional. A scale inhibitor or a small softener protects the heater; soap savings are modest.
Descale a coffee machine or kettle about every 3 months (typical manufacturer guidance for this hardness).
Estimates for planning, not a quote. Check your appliance manual for exact settings.
Dishwasher setting in Rio Vista
| Brand | Setting for this water |
|---|---|
| Bosch | H00 |
| Miele | 4 °dH |
| AEG / Electrolux | 2 |
| Beko | 1st |
| Hoover | S1 |
| LG | H1 |
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 Rio Vista water hard or soft?
It is moderately hard: 67 mg/L as CaCO₃ (3.9 gpg, 3.8 °dH). The usual bands are soft < 60, moderately hard 60–120, hard 120–180 and very hard > 180 mg/L.
Is tap water in Rio Vista 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 Rio Vista water?
3.9 gpg, equal to 3.8 °dH, 6.7 °fH or 67 mg/L calcium carbonate.
What dishwasher salt setting should I use in Rio Vista?
For 67 mg/L (3.8 °dH) check your manufacturer's table: level 2–3.
Do I need a water softener in Rio Vista?
Not essential; a scale inhibitor protects the heater cheaply.
Source
Source: California SWRCB Division of Drinking Water, EDT lab results, system CA4810004 (2026-03). Method: own measurement. California SWRCB Division of Drinking Water, EDT lab results, system CA4810004 · Outdated figure? Tell us