Water hardness in San Bruno
9.5 gpg hard
Tap water in San Bruno is hard: 9.5 gpg (163 mg/L · 9.1 °dH · 16.3 °fH).
Source: California SWRCB Division of Drinking Water, EDT lab results, system CA4110023 (2026-01) · data checked 2026-10-19
Range across supply zones: 148–309 mg/L.
The San Bruno figure comes from State Water Resources Control Board lab results for the City of San Bruno system. The median of 9 results from 2022 to 2026, taken at 4 well points, is 163 mg/L as CaCO3 (9.5 gpg), with a range of 147.8 to 308.8 mg/L. That is hard water. Expect visible scale on kettles and shower screens.
USGS classes: soft 0–60, moderately hard 61–120, hard 121–180, very hard >180 mg/L.
Water data
| Total hardness | 9.5 gpg |
|---|---|
| Utility | City Of San Bruno |
How San Bruno compares
- Tap water in San Bruno is 5 % harder than the median of the 1372 cities we track in the United States (9.1 gpg).
- By hardness it ranks 649 of 1372 in the United States (1 = hardest); 53 % of these cities have softer water.
- In California it is number 166 of 336 cities; the regional median is 9.5 gpg.
- Nearest city with clearly softer water: San Francisco, 17 km away (3.6 gpg).
- Nearest city with clearly harder water: South San Francisco, 4 km away (13 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 San Bruno
| 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 San Bruno water hard or soft?
It is hard: 163 mg/L as CaCO₃ (9.5 gpg, 9.1 °dH). The usual bands are soft < 60, moderately hard 60–120, hard 120–180 and very hard > 180 mg/L.
Is tap water in San Bruno 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 San Bruno water?
9.5 gpg, equal to 9.1 °dH, 16.3 °fH or 163 mg/L calcium carbonate.
What dishwasher salt setting should I use in San Bruno?
For 163 mg/L (9.1 °dH) check your manufacturer's table: level 4–5.
Do I need a water softener in San Bruno?
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 CA4110023 (2026-01). Method: own measurement. California SWRCB Division of Drinking Water, EDT lab results, system CA4110023 · Outdated figure? Tell us