Water hardness in Brentwood
21.8 gpg very hard
Tap water in Brentwood is very hard: 21.8 gpg (373 mg/L · 20.9 °dH · 37.3 °fH).
Source: California SWRCB Division of Drinking Water, EDT lab results, system CA0710004 (2025-12) · data checked 2026-10-19
Range across supply zones: 226–450 mg/L.
The Brentwood figure comes from State Water Resources Control Board lab results for the City of Brentwood system. The median of 36 results from 2021 to 2025, taken at wells and distribution points, is 373 mg/L as CaCO3 (21.8 gpg), with a range of 226 to 450 mg/L. Distribution samples alone read lower, so confidence in the exact figure is moderate. The water is very hard either way.
USGS classes: soft 0–60, moderately hard 61–120, hard 121–180, very hard >180 mg/L.
Water data
| Total hardness | 21.8 gpg |
|---|---|
| Utility | Brentwood |
How Brentwood compares
- Tap water in Brentwood is 141 % harder than the median of the 1372 cities we track in the United States (9.1 gpg).
- By hardness it ranks 86 of 1372 in the United States (1 = hardest); 94 % of these cities have softer water.
- In California it is number 22 of 336 cities; the regional median is 9.5 gpg.
- Nearest city with clearly softer water: Antioch, 8 km away (4.7 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 Brentwood
| Brand | Setting for this water |
|---|---|
| Bosch | H05 |
| Miele | 21 °dH |
| AEG / Electrolux | 5 |
| Beko | 6th |
| Hoover | S3 |
| LG | H4 |
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 Brentwood water hard or soft?
It is very hard: 373 mg/L as CaCO₃ (21.8 gpg, 20.9 °dH). The usual bands are soft < 60, moderately hard 60–120, hard 120–180 and very hard > 180 mg/L.
Is tap water in Brentwood 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 Brentwood water?
21.8 gpg, equal to 20.9 °dH, 37.3 °fH or 373 mg/L calcium carbonate.
What dishwasher salt setting should I use in Brentwood?
For 373 mg/L (20.9 °dH) check your manufacturer's table: maximum level (5–7).
Do I need a water softener in Brentwood?
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 CA0710004 (2025-12). Method: own measurement. California SWRCB Division of Drinking Water, EDT lab results, system CA0710004 · Outdated figure? Tell us