Water hardness in Arroyo Grande
20.4 gpg very hard
Tap water in Arroyo Grande is very hard: 20.4 gpg (350 mg/L · 19.6 °dH · 35 °fH).
Source: California SWRCB Division of Drinking Water, EDT lab results, system CA4010001 (2024-05) · data checked 2026-10-19
Range across supply zones: 104–470 mg/L.
The Arroyo Grande figure comes from State Water Resources Control Board lab results for the city utilities division. The median of 16 results from 2021 to 2024, taken at 8 well points, is 350 mg/L as CaCO3 (20.4 gpg), but results run from 104.1 to 470 mg/L. The water is very hard on median and varies by well. Scale builds fast, and a softener is worth considering.
USGS classes: soft 0–60, moderately hard 61–120, hard 121–180, very hard >180 mg/L.
Water data
| Total hardness | 20.4 gpg |
|---|---|
| Utility | City Of Arroyo Grande Utilities Division |
How Arroyo Grande compares
- Tap water in Arroyo Grande is 126 % harder than the median of the 1372 cities we track in the United States (9.1 gpg).
- By hardness it ranks 129 of 1372 in the United States (1 = hardest); 90 % of these cities have softer water.
- In California it is number 25 of 336 cities; the regional median is 9.5 gpg.
- Nearest city with clearly softer water: Grover Beach, 3 km away (11.7 gpg).
- Nearest city with clearly harder water: Pismo Beach, 9 km away (27.1 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 Arroyo Grande
| Brand | Setting for this water |
|---|---|
| Bosch | H05 |
| Miele | 20 °dH |
| AEG / Electrolux | 5 |
| 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 Arroyo Grande water hard or soft?
It is very hard: 350 mg/L as CaCO₃ (20.4 gpg, 19.6 °dH). The usual bands are soft < 60, moderately hard 60–120, hard 120–180 and very hard > 180 mg/L.
Is tap water in Arroyo Grande 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 Arroyo Grande water?
20.4 gpg, equal to 19.6 °dH, 35 °fH or 350 mg/L calcium carbonate.
What dishwasher salt setting should I use in Arroyo Grande?
For 350 mg/L (19.6 °dH) check your manufacturer's table: maximum level (5–7).
Do I need a water softener in Arroyo Grande?
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 CA4010001 (2024-05). Method: own measurement. California SWRCB Division of Drinking Water, EDT lab results, system CA4010001 · Outdated figure? Tell us