How hard is the water in San Marino, CA?

Tap water hardness
116mg/L
6.8gpg
Moderately hard

Reported by Cal/Am Water Company - San Marino · July 2025

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

San Marino water measures 116 mg/L (6.8 gpg) of hardness, moderately hard by USGS standards. The number comes from Cal/Am Water Company - San Marino, dated July 2025.

San Marino on the hardness scale, with nearby cities
060120180240300360+CA typical 121Rosemead: 46 mg/LRosemead 46Arcadia: 54 mg/LArcadia 54Temple City: 113 mg/LTemple City 113San Gabriel: 116 mg/LSan Gabriel 116South Pasadena: 128 mg/LSouth Pasadena 128Alhambra: 137 mg/LAlhambra 137Sierra Madre: 161 mg/LSierra Madre 161East San Gabriel: 192 mg/LEast San Gabriel 192East Pasadena: 192 mg/LEast Pasadena 192Pasadena: 230 mg/LPasadena 230San Marino 116mg/L as calcium carbonate060120180240300360+CA 121San Gabriel: 116 mg/LSan Gabriel 116South Pasadena: 128 mg/LSouth Pasa. 128Alhambra: 137 mg/LAlhambra 137East San Gabriel: 192 mg/LEast San G. 192East Pasadena: 192 mg/LEast Pasad. 192Pasadena: 230 mg/LPasadena 230116 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 Marino sits close to the typical California figure of 121 mg/L. Of the 10 nearest cities we track, 3 have softer water and 6 have harder. The range nearby runs from 46 mg/L in Rosemead to 230 in Pasadena.

What 116 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 San Marino

3 people × 75 gallons a day × 6.8 gpg = 1,532 grains a day. A 24,000-grain unit regenerates about every 15 days.

Size it for your household

EPA record for San Marino's water system

Cal/Am Water Company - San Marino · PWSID CA1910139

No health-based violations since 2016

Serves about 48,065 people from surface water.

Health-based
0
Monitoring or reporting
1
Open now
0

TapWaterData ties San Marino to this system. EPA's service-area records do not name San Marino, 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 Marino water hard?

Somewhat. It measures about 116 mg/L (6.8 grains per gallon), which the USGS classes as moderately hard.

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

About 6.8 gpg. One grain per gallon equals 17.1 mg/L, so 116 mg/L divided by 17.1 gives 6.8.

What size water softener do I need in San Marino?

For 3 people using 75 gallons each per day, 6.8 gpg works out to about 1,532 grains a day. A 24,000-grain softener covers that with a regeneration about every 15 days.

Has the San Marino water system had EPA violations?

EPA records show no health-based violations for Cal/Am Water Company - San Marino 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, July 21, 2025), CC BY 4.0. Population: US Census Bureau. Violations: EPA ECHO. How we use them.