How hard is the water in South Monrovia Island, CA?

Tap water hardness
75mg/L
4.4gpg
Moderately hard

Reported by Cal-Am Water Company - Duarte · July 2025

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

South Monrovia Island water measures 75 mg/L (4.4 gpg) of hardness, moderately hard by USGS standards. The number comes from Cal-Am Water Company - Duarte, dated July 2025.

South Monrovia Island on the hardness scale, with nearby cities
060120180240300360+CA typical 121El Monte: 48 mg/LEl Monte 48Arcadia: 54 mg/LArcadia 54Duarte: 75 mg/LDuarte 75Vincent: 112 mg/LVincent 112Temple City: 113 mg/LTemple City 113Mayflower Village: 135 mg/LMayflower Village 135Monrovia: 135 mg/LMonrovia 135Sierra Madre: 161 mg/LSierra Madre 161East Pasadena: 192 mg/LEast Pasadena 192East San Gabriel: 192 mg/LEast San Gabriel 192South Monrovia Island 75mg/L as calcium carbonate060120180240300360+CA 121El Monte: 48 mg/LEl Monte 48Arcadia: 54 mg/LArcadia 54Duarte: 75 mg/LDuarte 75Temple City: 113 mg/LTemple City 113Mayflower Village: 135 mg/LMayflower. 135Monrovia: 135 mg/LMonrovia 13575 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 75 mg/L, South Monrovia Island is 46 mg/L below the typical California figure of 121. Of the 10 nearest cities we track, 2 have softer water and 7 have harder. The range nearby runs from 48 mg/L in El Monte to 192 in East Pasadena.

What 75 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 South Monrovia Island

3 people × 75 gallons a day × 4.4 gpg = 983 grains a day. A 24,000-grain unit regenerates about every 24 days.

Size it for your household

EPA record for South Monrovia Island's water system

Cal-Am Water Company - Duarte · PWSID CA1910186

No health-based violations since 2016

Serves about 24,767 people from groundwater.

Health-based
0
Monitoring or reporting
0
Open now
0

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

Somewhat. It measures about 75 mg/L (4.4 grains per gallon), which the USGS classes as moderately hard.

What is the water hardness in South Monrovia Island in grains per gallon?

About 4.4 gpg. One grain per gallon equals 17.1 mg/L, so 75 mg/L divided by 17.1 gives 4.4.

What size water softener do I need in South Monrovia Island?

For 3 people using 75 gallons each per day, 4.4 gpg works out to about 983 grains a day. A 24,000-grain softener covers that with a regeneration about every 24 days.

Has the South Monrovia Island water system had EPA violations?

EPA records show no health-based violations for Cal-Am Water Company - Duarte since 2016.

Nearby cities

All 515 cities in California

Hardness data: TapWaterData US Water Hardness (utility report, July 8, 2025), CC BY 4.0. Population: US Census Bureau. Violations: EPA ECHO. How we use them.