Water hardness in Pomona
15.5 gpg very hard
Tap water in Pomona is very hard: 15.5 gpg (265 mg/L · 14.8 °dH · 26.5 °fH).
Source: California SWRCB Division of Drinking Water, EDT lab results, system CA1910126 (2026-04) · data checked 2026-10-19
Range across supply zones: 163–307 mg/L.
The Pomona figure comes from State Water Resources Control Board lab results for the City of Pomona system, using finished-water samples. The median of 44 results from 2021 to 2026 is 265 mg/L as CaCO3 (15.5 gpg), with a range of 163 to 307 mg/L. This is very hard water. Expect heavy scale on heaters and glassware, and consider a softener.
USGS classes: soft 0–60, moderately hard 61–120, hard 121–180, very hard >180 mg/L.
Water data
| Total hardness | 15.5 gpg |
|---|---|
| Utility | Pomona - City, Water Dept. |
How Pomona compares
- Tap water in Pomona is 71 % harder than the median of the 1372 cities we track in the United States (9.1 gpg).
- By hardness it ranks 345 of 1372 in the United States (1 = hardest); 75 % of these cities have softer water.
- In California it is number 63 of 336 cities; the regional median is 9.5 gpg.
- Nearest city with clearly softer water: Diamond Bar, 6 km away (9.7 gpg).
- Nearest city with clearly harder water: Anaheim, 23 km away (19.5 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 Pomona
| Brand | Setting for this water |
|---|---|
| Bosch | H04 |
| Miele | 15 °dH |
| AEG / Electrolux | 4 |
| Beko | 4th |
| 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 Pomona water hard or soft?
It is very hard: 265 mg/L as CaCO₃ (15.5 gpg, 14.8 °dH). The usual bands are soft < 60, moderately hard 60–120, hard 120–180 and very hard > 180 mg/L.
Is tap water in Pomona 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 Pomona water?
15.5 gpg, equal to 14.8 °dH, 26.5 °fH or 265 mg/L calcium carbonate.
What dishwasher salt setting should I use in Pomona?
For 265 mg/L (14.8 °dH) check your manufacturer's table: maximum level (5–7).
Do I need a water softener in Pomona?
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 CA1910126 (2026-04). Method: own measurement. California SWRCB Division of Drinking Water, EDT lab results, system CA1910126 · Outdated figure? Tell us