Millbrae, 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 Millbrae 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.

Millbrae 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 37San Bruno: 44 mg/LSan Bruno 44El Granada: 46 mg/LEl Granada 46South San Francisco: 64 mg/LSouth San Francisco 64Pacifica: 70 mg/LPacifica 70Daly City: 73 mg/LDaly City 73Millbrae 44mg/L as calcium carbonate060120180240300360+CA 121Burlingame: 31 mg/LBurlingame 31San Mateo: 35 mg/LSan Mateo 35Hillsborough: 36 mg/LHillsborou. 36San Bruno: 44 mg/LSan Bruno 44South San Francisco: 64 mg/LSouth San. 64Pacifica: 70 mg/LPacifica 7044 mg/Lmg/L as calcium carbonate
Soft 0–60 mg/LModerately hard 61–120 mg/LHard 121–180 mg/LVery hard 181+ mg/L

At 44 mg/L, Millbrae is 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 Millbrae's water system

City of Millbrae · PWSID CA4110018

No health-based violations since 2016

Serves about 22,795 people from surface water.

Health-based
0
Monitoring or reporting
1
Open now
0

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 Millbrae 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 Millbrae 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 Millbrae water system had EPA violations?

EPA records show no health-based violations for City of Millbrae since 2016. There were also 1 monitoring or reporting violation, which are about late or missing tests and notices.

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.