Water hardness in Sunnyvale CA
5.7 gpg moderately hard
Tap water in Sunnyvale CA is moderately hard: 5.7 gpg (97 mg/L · 5.4 °dH · 9.7 °fH).
Source: City of Sunnyvale Water Quality Report 2025 (2025) · data checked 2026-10-19
Range across supply zones: 8–310 mg/L.
3 supply zones — hardness varies by neighbourhood; the figure above is the median.
Hardness by district / supply zone
| gpg | mg/L | ||
|---|---|---|---|
| City wells (groundwater) | 16.9 | 290 | very hard |
| SFPUC supply (north Sunnyvale) | 3.5 | 60 | moderately hard |
| Valley Water supply (far southwest Sunnyvale) | 5.7 | 97 | moderately hard |
Sunnyvale's 2025 report lists three supplies. City wells in most of the city average 290 mg/L (17.0 gpg), Valley Water in the far southwest averages 97 mg/L, and SFPUC water in the north averages 60 mg/L (range 8.1 to 112). The page shows the median of 97 mg/L (5.7 gpg). Wells supply most of the city, so many addresses get much harder water than that figure.
USGS classes: soft 0–60, moderately hard 61–120, hard 121–180, very hard >180 mg/L.
Water data
| Total hardness | 5.7 gpg |
|---|---|
| Utility | City of Sunnyvale (Water Operations) |
How Sunnyvale CA compares
- Tap water in Sunnyvale CA is 37 % softer than the median of the 1372 cities we track in the United States (9.1 gpg).
- By hardness it ranks 1037 of 1372 in the United States (1 = hardest); 24 % of these cities have softer water.
- In California it is number 254 of 336 cities; the regional median is 9.5 gpg.
- Nearest city with clearly softer water: Hayward, 29 km away (3.5 gpg).
- Nearest city with clearly harder water: Los Altos, 5 km away (18.1 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 Sunnyvale CA
| Brand | Setting for this water |
|---|---|
| Bosch | H00 |
| Miele | 5 °dH |
| AEG / Electrolux | 2 |
| Beko | 2nd |
| 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 Sunnyvale CA water hard or soft?
It is moderately hard: 97 mg/L as CaCO₃ (5.7 gpg, 5.4 °dH). The usual bands are soft < 60, moderately hard 60–120, hard 120–180 and very hard > 180 mg/L.
Is tap water in Sunnyvale CA 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 Sunnyvale CA water?
5.7 gpg, equal to 5.4 °dH, 9.7 °fH or 97 mg/L calcium carbonate.
What dishwasher salt setting should I use in Sunnyvale CA?
For 97 mg/L (5.4 °dH) check your manufacturer's table: level 2–3.
Do I need a water softener in Sunnyvale CA?
Not essential; a scale inhibitor protects the heater cheaply.
Source
Source: City of Sunnyvale Water Quality Report 2025 (2025). Method: figure published by the water supplier. City of Sunnyvale Water Quality Report 2025 · Outdated figure? Tell us