San Francisco, CA water hardness

Tap water hardness
25mg/L
1.5gpg
SoftReports range 1–25

Reported by SFPUC City Distribution Division · October 2025

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

Tap water in San Francisco has about 25 mg/L of hardness, which is 1.5 grains per gallon. On the USGS scale that counts as soft. The number comes from SFPUC City Distribution Division, dated October 2025. Reports for this system disagree, with values from 1 to 25 mg/L.

San Francisco on the hardness scale, with nearby cities
060120180240300360+CA typical 121Tamalpais-Homestead Valley: 56 mg/LTamalpais-Homestead Valley 56Mill Valley: 56 mg/LMill Valley 56Kentfield: 56 mg/LKentfield 56Fairfax: 56 mg/LFairfax 56Strawberry: 56 mg/LStrawberry 56San Anselmo: 56 mg/LSan Anselmo 56Sausalito: 56 mg/LSausalito 56Larkspur: 56 mg/LLarkspur 56Pacifica: 70 mg/LPacifica 70Daly City: 73 mg/LDaly City 73San Francisco 25mg/L as calcium carbonate060120180240300360+CA 121Tamalpais-Homestead Valley: 56 mg/LTamalpais-. 56Mill Valley: 56 mg/LMill Valley 56Kentfield: 56 mg/LKentfield 56Fairfax: 56 mg/LFairfax 56Strawberry: 56 mg/LStrawberry 56San Anselmo: 56 mg/LSan Anselmo 5625 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 Francisco sits 96 mg/L below the typical California figure of 121. None of the 10 nearest cities we track has softer water. The range nearby runs from 56 mg/L in Tamalpais-Homestead Valley to 73 in Daly City.

What 25 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 25 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 Francisco's water system

SFPUC City Distribution Division · PWSID CA3810011

No health-based violations since 2016

Serves about 848,019 people from surface water.

Health-based
0
Monitoring or reporting
0
Open now
0

TapWaterData ties San Francisco to this system. EPA's service-area records do not name San Francisco, so check the utility printed on your water bill.

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 Francisco water hard?

No. It measures about 25 mg/L (1.5 grains per gallon), which the USGS classes as soft.

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

About 1.5 gpg. One grain per gallon equals 17.1 mg/L, so 25 mg/L divided by 17.1 gives 1.5.

Has the San Francisco water system had EPA violations?

EPA records show no health-based violations for SFPUC City Distribution Division since 2016.

Nearby cities

All 515 cities in California

Hardness data: TapWaterData US Water Hardness (utility report, October 13, 2025), CC BY 4.0. Population: US Census Bureau. Violations: EPA ECHO. How we use them.