Water hardness in Clearlake
10.4 gpg hard
Tap water in Clearlake is hard: 10.4 gpg (178 mg/L · 9.9 °dH · 17.8 °fH).
Source: California SWRCB Division of Drinking Water, EDT lab results, system CA1710002 (2026-05) · data checked 2026-10-19
Range across supply zones: 130–219 mg/L.
The figure is for the Golden State Water Company Clearlake system, which serves only a small part of the city, from State Water Resources Control Board lab results. The median of 8 results from 2021 to 2026 is 177.5 mg/L as CaCO3 (10.4 gpg), with a range of 130 to 218.7 mg/L. Other suppliers cover the rest. Where it applies, the water is hard.
USGS classes: soft 0–60, moderately hard 61–120, hard 121–180, very hard >180 mg/L.
Water data
| Total hardness | 10.4 gpg |
|---|---|
| Utility | Golden State Water Co.-Clearlake System |
How Clearlake compares
- Tap water in Clearlake is 14 % harder than the median of the 1372 cities we track in the United States (9.1 gpg).
- By hardness it ranks 606 of 1372 in the United States (1 = hardest); 56 % of these cities have softer water.
- In California it is number 150 of 336 cities; the regional median is 9.5 gpg.
- Nearest city with clearly softer water: Lakeport, 26 km away (6.3 gpg).
- Nearest city with clearly harder water: Dunnigan, 58 km away (16.9 gpg).
Ranking of the hardest and softest water in the United States →
What it means at home
- Fast scale on taps, shower screens and kettle; white spots on glassware.
- Water heater: efficiency loss and element failures within years if unprotected.
- Dry skin and dull hair after showering are common.
- Softener recommended; jug or reverse osmosis for drinking.
How much salt will you use for softening?
Recommended, especially with a heater or boiler: scale cuts efficiency and shortens its life.
Descale a coffee machine or kettle about every 2 months (typical manufacturer guidance for this hardness).
Estimates for planning, not a quote. Check your appliance manual for exact settings.
Dishwasher setting in Clearlake
| Brand | Setting for this water |
|---|---|
| Bosch | H02 |
| Miele | 10 °dH |
| AEG / Electrolux | 2 |
| Beko | 3rd |
| Hoover | S2 |
| LG | H2 |
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 Clearlake water hard or soft?
It is hard: 178 mg/L as CaCO₃ (10.4 gpg, 9.9 °dH). The usual bands are soft < 60, moderately hard 60–120, hard 120–180 and very hard > 180 mg/L.
Is tap water in Clearlake 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 Clearlake water?
10.4 gpg, equal to 9.9 °dH, 17.8 °fH or 178 mg/L calcium carbonate.
What dishwasher salt setting should I use in Clearlake?
For 178 mg/L (9.9 °dH) check your manufacturer's table: level 4–5.
Do I need a water softener in Clearlake?
Recommended if you have a water heater, boiler or tankless unit: it saves repairs and detergent.
Source
Source: California SWRCB Division of Drinking Water, EDT lab results, system CA1710002 (2026-05). Method: own measurement. California SWRCB Division of Drinking Water, EDT lab results, system CA1710002 · Outdated figure? Tell us