San Bruno, CA water hardness

Tap water hardness
44mg/L
2.6gpg
Soft

Reported by City of Millbrae · August 2025

CA typical
121 mg/L
EPA health violations since 2016
0
Data
Utility report

Tap water in San Bruno has about 44 mg/L of hardness, which is 2.6 grains per gallon. On the USGS scale that counts as soft. The number comes from City of Millbrae, dated August 2025.

San Bruno on the hardness scale, with nearby cities
060120180240300360+CA typical 121Burlingame: 31 mg/LBurlingame 31Foster City: 33 mg/LFoster City 33San Mateo: 35 mg/LSan Mateo 35Hillsborough: 36 mg/LHillsborough 36Belmont: 37 mg/LBelmont 37Millbrae: 44 mg/LMillbrae 44El Granada: 46 mg/LEl Granada 46South San Francisco: 64 mg/LSouth San Francisco 64Pacifica: 70 mg/LPacifica 70Daly City: 73 mg/LDaly City 73San Bruno 44mg/L as calcium carbonate060120180240300360+CA 121Burlingame: 31 mg/LBurlingame 31Hillsborough: 36 mg/LHillsborou. 36Millbrae: 44 mg/LMillbrae 44South San Francisco: 64 mg/LSouth San. 64Pacifica: 70 mg/LPacifica 70Daly City: 73 mg/LDaly City 7344 mg/Lmg/L as calcium carbonate
Soft 0–60 mg/LModerately hard 61–120 mg/LHard 121–180 mg/LVery hard 181+ mg/L

San Bruno sits 77 mg/L below the typical California figure of 121. Of the 10 nearest cities we track, 5 have softer water and 4 have harder. The range nearby runs from 31 mg/L in Burlingame to 73 in Daly City.

What 44 mg/L means at home

Soap and shampoo lather with very little product. Kettles and showerheads stay mostly free of white crust.

Some people notice that soap feels slow to rinse off in soft water. That slippery feel is normal and harmless.

Hardness is not a health problem, and EPA sets no limit for it. It is a matter of scale and soap.

What to do about it

Nothing, as far as hardness goes. At 44 mg/L a softener would have almost nothing to remove.

Carbon filter

If the water tastes of chlorine, a pitcher or faucet carbon filter takes care of that. It does not change hardness.

EPA record for San Bruno's water system

City of San Bruno · PWSID CA4110023

No health-based violations since 2016

Serves about 42,631 people from surface water.

Health-based
0
Monitoring or reporting
0
Open now
0

EPA lists City of San Bruno as the system serving San Bruno. The hardness figure above comes from a different system's report, which TapWaterData uses for San Bruno.

Health-based means a contaminant above its legal limit or a missed treatment step. Monitoring and reporting violations are late or missing tests and notices. Source: EPA ECHO, 2026Q3 export, violations with periods starting 2016 or later. Full EPA record.

Questions

Is San Bruno water hard?

No. It measures about 44 mg/L (2.6 grains per gallon), which the USGS classes as soft.

What is the water hardness in San Bruno in grains per gallon?

About 2.6 gpg. One grain per gallon equals 17.1 mg/L, so 44 mg/L divided by 17.1 gives 2.6.

Has the San Bruno water system had EPA violations?

EPA records show no health-based violations for City of San Bruno since 2016.

Nearby cities

All 515 cities in California

Hardness data: TapWaterData US Water Hardness (utility report, August 26, 2025), CC BY 4.0. Population: US Census Bureau. Violations: EPA ECHO. How we use them.