Water hardness in Colton
12 gpg very hard
Tap water in Colton is very hard: 12 gpg (205 mg/L · 11.5 °dH · 20.5 °fH).
Source: California SWRCB Division of Drinking Water, EDT lab results, system CA3610014 (2025-09) · data checked 2026-10-19
Range across supply zones: 150–241 mg/L.
The Colton figure comes from State Water Resources Control Board lab results for the City of Colton system. The median of 30 results from 2021 to 2025, taken at 11 treatment-plant and well points, is 205 mg/L as CaCO3 (12.0 gpg), with a range of 150 to 241 mg/L. This is very hard water. Scale builds quickly on heaters and fixtures.
USGS classes: soft 0–60, moderately hard 61–120, hard 121–180, very hard >180 mg/L.
Water data
| Total hardness | 12 gpg |
|---|---|
| Utility | Colton, City Of |
How Colton compares
- Tap water in Colton is 32 % harder than the median of the 1372 cities we track in the United States (9.1 gpg).
- By hardness it ranks 512 of 1372 in the United States (1 = hardest); 62 % of these cities have softer water.
- In California it is number 117 of 336 cities; the regional median is 9.5 gpg.
- Nearest city with clearly softer water: Rialto, 9 km away (9.3 gpg).
- Nearest city with clearly harder water: Pomona, 40 km away (15.5 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 Colton
| Brand | Setting for this water |
|---|---|
| Bosch | H03 |
| Miele | 11 °dH |
| AEG / Electrolux | 3 |
| 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 Colton water hard or soft?
It is very hard: 205 mg/L as CaCO₃ (12 gpg, 11.5 °dH). The usual bands are soft < 60, moderately hard 60–120, hard 120–180 and very hard > 180 mg/L.
Is tap water in Colton 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 Colton water?
12 gpg, equal to 11.5 °dH, 20.5 °fH or 205 mg/L calcium carbonate.
What dishwasher salt setting should I use in Colton?
For 205 mg/L (11.5 °dH) check your manufacturer's table: maximum level (5–7).
Do I need a water softener in Colton?
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 CA3610014 (2025-09). Method: own measurement. California SWRCB Division of Drinking Water, EDT lab results, system CA3610014 · Outdated figure? Tell us