Hard water in Santa Clara, CA
Reported by City of Santa Clara · October 2025
- CA typical
- 121 mg/L
- EPA health violations since 2016
- 0
- Softener for 3 people
- 24k grain
- Data
- Utility report
Santa Clara water measures 248 mg/L (14.5 gpg) of hardness, very hard by USGS standards. The number comes from City of Santa Clara, dated October 2025.
At 248 mg/L, Santa Clara is 127 mg/L above the typical California figure of 121. Of the 10 nearest cities we track, 8 have softer water and 2 have harder. The range nearby runs from 49 mg/L in Milpitas to 298 in Sunnyvale.
What 248 mg/L means at home
Scale forms fast here. Kettles and coffee makers need regular descaling, and showerheads clog unless you clean them.
Tank water heaters collect mineral sediment that insulates the water from the burner, so flushing the tank matters more than usual.
Dishes and glass shower doors spot easily. Soap scum and a dull film on hair or laundry are common complaints.
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
At 248 mg/L most of the trouble is scale, and only a few things deal with it.
Ion-exchange water softener
The standard whole-house fix. It swaps calcium and magnesium for sodium or potassium and needs salt plus a drain. Size it with the calculator below.
Salt-free conditioner
No salt and no drain line. It changes how minerals form scale instead of removing them, so water still tests hard.
Reverse osmosis or carbon filter
Under-sink reverse osmosis removes minerals from drinking water only. Plain carbon filters improve taste but do not soften.
3 people × 75 gallons a day × 14.5 gpg = 3,262 grains a day. A 24,000-grain unit regenerates about every 7 days.
EPA record for Santa Clara's water system
No health-based violations since 2016
Serves about 134,587 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 Santa Clara water hard?
Yes. It measures about 248 mg/L (14.5 grains per gallon), which the USGS classes as very hard.
What is the water hardness in Santa Clara in grains per gallon?
About 14.5 gpg. One grain per gallon equals 17.1 mg/L, so 248 mg/L divided by 17.1 gives 14.5.
What size water softener do I need in Santa Clara?
For 3 people using 75 gallons each per day, 14.5 gpg works out to about 3,262 grains a day. A 24,000-grain softener covers that with a regeneration about every 7 days.
Has the Santa Clara water system had EPA violations?
EPA records show no health-based violations for City of Santa Clara since 2016.
Nearby cities
- Sunnyvale298 mg/LVery hard
- Cupertino186 mg/LVery hard
- Campbell178 mg/LHard
- Milpitas49 mg/LSoft
- Mountain View134 mg/LHard
- Los Altos298 mg/LVery hard
- Saratoga178 mg/LHard
- Alum Rock178 mg/LHard
- East Foothills178 mg/LHard
- Fremont65 mg/LModerately hard
Hardness data: TapWaterData US Water Hardness (utility report, October 7, 2025), CC BY 4.0. Population: US Census Bureau. Violations: EPA ECHO. How we use them.