Water hardness in Monterey
9.3 gpg hard
Tap water in Monterey is hard: 9.3 gpg (160 mg/L · 9 °dH · 16 °fH).
Source: California SWRCB Division of Drinking Water, EDT lab results, system CA2710004 (2025-09) · data checked 2026-10-19
Range across supply zones: 130–210 mg/L.
The figure is for the California American Water system in Monterey, from State Water Resources Control Board lab results. The median of 31 results from 2021 to 2025, taken at 13 points, is 160 mg/L as CaCO3 (9.3 gpg), with a range of 130 to 210 mg/L. A few plant-only readings in the file look treated or mislabeled, and we ignore them. Confidence is moderate. 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 | 9.3 gpg |
|---|---|
| Utility | Cal Am Water Company - Monterey |
How Monterey compares
- Tap water in Monterey is close to the median of the 1372 cities we track in the United States (9.1 gpg).
- By hardness it ranks 664 of 1372 in the United States (1 = hardest); 51 % of these cities have softer water.
- In California it is number 171 of 336 cities; the regional median is 9.5 gpg.
- Nearest city with clearly softer water: Greenfield, 65 km away (7.3 gpg).
- Nearest city with clearly harder water: Marina, 12 km away (12 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 Monterey
| Brand | Setting for this water |
|---|---|
| Bosch | H02 |
| Miele | 9 °dH |
| AEG / Electrolux | 2 |
| Beko | 3rd |
| Hoover | S1 |
| 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 Monterey water hard or soft?
It is hard: 160 mg/L as CaCO₃ (9.3 gpg, 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 Monterey 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 Monterey water?
9.3 gpg, equal to 9 °dH, 16 °fH or 160 mg/L calcium carbonate.
What dishwasher salt setting should I use in Monterey?
For 160 mg/L (9 °dH) check your manufacturer's table: level 4–5.
Do I need a water softener in Monterey?
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 CA2710004 (2025-09). Method: own measurement. California SWRCB Division of Drinking Water, EDT lab results, system CA2710004 · Outdated figure? Tell us