How hard is the water in Fremont, CA?

Tap water hardness
65mg/L
3.8gpg
Moderately hardReports range 44–65

Reported by Alameda County Water District · October 2025

CA typical
121 mg/L
EPA health violations since 2016
0
Softener for 3 people
24k grain
Data
Utility report

Tap water in Fremont has about 65 mg/L of hardness, which is 3.8 grains per gallon. On the USGS scale that counts as moderately hard. The number comes from Alameda County Water District, dated October 2025. Reports for this system disagree, with values from 44 to 65 mg/L.

Fremont on the hardness scale, with nearby cities
060120180240300360+CA typical 121Menlo Park: 46 mg/LMenlo Park 46Milpitas: 49 mg/LMilpitas 49Newark: 65 mg/LNewark 65Union City: 65 mg/LUnion City 65Mountain View: 134 mg/LMountain View 134East Foothills: 178 mg/LEast Foothills 178Alum Rock: 178 mg/LAlum Rock 178Santa Clara: 248 mg/LSanta Clara 248Sunnyvale: 298 mg/LSunnyvale 298Los Altos: 298 mg/LLos Altos 298Fremont 65mg/L as calcium carbonate060120180240300360+CA 121Milpitas: 49 mg/LMilpitas 49Newark: 65 mg/LNewark 65Union City: 65 mg/LUnion City 65Mountain View: 134 mg/LMountain V. 134Santa Clara: 248 mg/LSanta Clara 248Sunnyvale: 298 mg/LSunnyvale 29865 mg/Lmg/L as calcium carbonate
Soft 0–60 mg/LModerately hard 61–120 mg/LHard 121–180 mg/LVery hard 181+ mg/L

Fremont sits 56 mg/L below the typical California figure of 121. Of the 10 nearest cities we track, 2 have softer water and 6 have harder. The range nearby runs from 46 mg/L in Menlo Park to 298 in Sunnyvale.

What 65 mg/L means at home

You may see faint white spots on glasses and shower doors after the water dries.

Scale builds up slowly. A kettle or coffee maker needs descaling now and then, maybe every few months.

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

Optional. Plenty of households at this level live with it and descale the kettle now and then.

Water softener

Worth a look if spots on glass bother you, or if your tankless water heater manual asks for softer water.

Carbon filter

Improves taste and removes chlorine. It leaves calcium and magnesium in place.

Softener size for Fremont

3 people × 75 gallons a day × 3.8 gpg = 857 grains a day. A 24,000-grain unit regenerates about every 27 days.

Size it for your household

EPA record for Fremont's water system

Alameda County Water District · PWSID CA0110001

No health-based violations since 2016

Serves about 344,000 people from surface water.

Health-based
0
Monitoring or reporting
0
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 Fremont water hard?

Somewhat. It measures about 65 mg/L (3.8 grains per gallon), which the USGS classes as moderately hard.

What is the water hardness in Fremont in grains per gallon?

About 3.8 gpg. One grain per gallon equals 17.1 mg/L, so 65 mg/L divided by 17.1 gives 3.8.

What size water softener do I need in Fremont?

For 3 people using 75 gallons each per day, 3.8 gpg works out to about 857 grains a day. A 24,000-grain softener covers that with a regeneration about every 27 days.

Has the Fremont water system had EPA violations?

EPA records show no health-based violations for Alameda County Water District since 2016.

Nearby cities

All 515 cities in California

Hardness data: TapWaterData US Water Hardness (utility report, October 4, 2025), CC BY 4.0. Population: US Census Bureau. Violations: EPA ECHO. How we use them.