Water hardness in Simi Valley
17.4 gpg very hard
Tap water in Simi Valley is very hard: 17.4 gpg (298 mg/L · 16.7 °dH · 29.8 °fH).
Source: California SWRCB Division of Drinking Water, EDT lab results, system CA5610023 (2026-06) · data checked 2026-10-19
Range across supply zones: 184–1012 mg/L.
2 supply zones — hardness varies by neighbourhood; the figure above is the median.
Hardness by district / supply zone
| gpg | mg/L | ||
|---|---|---|---|
| Golden State Water Company - Simi Valley | 23.4 | 400 | very hard |
| Ventura Wwd No. 8 - Simi Valley | 11.4 | 195 | very hard |
The Simi Valley figure comes from State Water Resources Control Board lab results for Ventura Waterworks District No. 8. The median of 266 results from 2021 to 2026 is 195 mg/L as CaCO3 (11.4 gpg), within a range of 184 to 535.5 mg/L. The top value is a single high result, not a typical tap. This is very hard water, and scale builds quickly on heaters.
USGS classes: soft 0–60, moderately hard 61–120, hard 121–180, very hard >180 mg/L.
Water data
| Total hardness | 17.4 gpg |
|---|---|
| Utility | Ventura Wwd No. 8 - Simi Valley |
How Simi Valley compares
- Tap water in Simi Valley is 92 % harder than the median of the 1372 cities we track in the United States (9.1 gpg).
- By hardness it ranks 260 of 1372 in the United States (1 = hardest); 81 % of these cities have softer water.
- In California it is number 48 of 336 cities; the regional median is 9.5 gpg.
- Nearest city with clearly softer water: Thousand Oaks, 14 km away (8.2 gpg).
- Nearest city with clearly harder water: Piru, 17 km away (37.8 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 Simi Valley
| Brand | Setting for this water |
|---|---|
| Bosch | H05 |
| Miele | 17 °dH |
| AEG / Electrolux | 4 |
| Beko | 5th |
| Hoover | S2 |
| 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 Simi Valley water hard or soft?
It is very hard: 298 mg/L as CaCO₃ (17.4 gpg, 16.7 °dH). The usual bands are soft < 60, moderately hard 60–120, hard 120–180 and very hard > 180 mg/L.
Is tap water in Simi Valley 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 Simi Valley water?
17.4 gpg, equal to 16.7 °dH, 29.8 °fH or 298 mg/L calcium carbonate.
What dishwasher salt setting should I use in Simi Valley?
For 298 mg/L (16.7 °dH) check your manufacturer's table: maximum level (5–7).
Do I need a water softener in Simi Valley?
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 CA5610023 (2026-06). Method: own measurement. California SWRCB Division of Drinking Water, EDT lab results, system CA5610023 · Outdated figure? Tell us