Water hardness in Downey
15.5 gpg very hard
Tap water in Downey is very hard: 15.5 gpg (266 mg/L · 14.9 °dH · 26.6 °fH).
Source: California SWRCB Division of Drinking Water, EDT lab results, system CA1910034 (2026-04) · data checked 2026-10-19
Range across supply zones: 182–312 mg/L.
The Downey figure comes from State Water Resources Control Board lab results for the City of Downey water department. The median of 36 results from 2021 to 2026 is 265.5 mg/L as CaCO3 (15.5 gpg), with a range of 182 to 312 mg/L. The 18 sampling points are listed as wells. This is very hard water, and 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 | 15.5 gpg |
|---|---|
| Utility | Downey - City, Water Dept. |
How Downey compares
- Tap water in Downey is 71 % harder than the median of the 1372 cities we track in the United States (9.1 gpg).
- By hardness it ranks 344 of 1372 in the United States (1 = hardest); 75 % of these cities have softer water.
- In California it is number 62 of 336 cities; the regional median is 9.5 gpg.
- Nearest city with clearly softer water: Bell Gardens, 4 km away (8.2 gpg).
- Nearest city with clearly harder water: Monterey Park, 12 km away (22.2 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 Downey
| 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 Downey water hard or soft?
It is very hard: 266 mg/L as CaCO₃ (15.5 gpg, 14.9 °dH). The usual bands are soft < 60, moderately hard 60–120, hard 120–180 and very hard > 180 mg/L.
Is tap water in Downey 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 Downey water?
15.5 gpg, equal to 14.9 °dH, 26.6 °fH or 266 mg/L calcium carbonate.
What dishwasher salt setting should I use in Downey?
For 266 mg/L (14.9 °dH) check your manufacturer's table: maximum level (5–7).
Do I need a water softener in Downey?
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 CA1910034 (2026-04). Method: own measurement. California SWRCB Division of Drinking Water, EDT lab results, system CA1910034 · Outdated figure? Tell us