How hard is the water in Rialto, CA?

Tap water hardness
89mg/L
5.2gpg
Moderately hardReports range 69–150

Reported by San Gabriel Valley WC - Fontana · August 2025

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

Tap water in Rialto has about 89 mg/L of hardness, which is 5.2 grains per gallon. On the USGS scale that counts as moderately hard. The number comes from San Gabriel Valley WC - Fontana, dated August 2025. Reports for this system disagree, with values from 69 to 150 mg/L.

Rialto on the hardness scale, with nearby cities
060120180240300360+CA typical 121Rancho Cucamonga: 68 mg/LRancho Cucamonga 68Muscoy: 72 mg/LMuscoy 72San Bernardino: 79 mg/LSan Bernardino 79Fontana: 92 mg/LFontana 92Bloomington: 96 mg/LBloomington 96Highgrove: 99 mg/LHighgrove 99Loma Linda: 99 mg/LLoma Linda 99Jurupa Valley: 122 mg/LJurupa Valley 122Grand Terrace: 137 mg/LGrand Terrace 137Colton: 139 mg/LColton 139Rialto 89mg/L as calcium carbonate060120180240300360+CA 121Muscoy: 72 mg/LMuscoy 72San Bernardino: 79 mg/LSan Bernar. 79Fontana: 92 mg/LFontana 92Bloomington: 96 mg/LBloomington 96Grand Terrace: 137 mg/LGrand Terr. 137Colton: 139 mg/LColton 13989 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 89 mg/L, Rialto is 32 mg/L below the typical California figure of 121. Of the 10 nearest cities we track, 3 have softer water and 7 have harder. The range nearby runs from 68 mg/L in Rancho Cucamonga to 139 in Colton.

What 89 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 Rialto

3 people × 75 gallons a day × 5.2 gpg = 1,170 grains a day. A 24,000-grain unit regenerates about every 20 days.

Size it for your household

EPA record for Rialto's water system

Rialto, City of · PWSID CA3610038

No health-based violations since 2016

Serves about 59,264 people from surface water.

Health-based
0
Monitoring or reporting
0
Open now
0

EPA lists Rialto, City of as the system serving Rialto. The hardness figure above comes from a different system's report, which TapWaterData uses for Rialto.

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 Rialto water hard?

Somewhat. It measures about 89 mg/L (5.2 grains per gallon), which the USGS classes as moderately hard.

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

About 5.2 gpg. One grain per gallon equals 17.1 mg/L, so 89 mg/L divided by 17.1 gives 5.2.

What size water softener do I need in Rialto?

For 3 people using 75 gallons each per day, 5.2 gpg works out to about 1,170 grains a day. A 24,000-grain softener covers that with a regeneration about every 20 days.

Has the Rialto water system had EPA violations?

EPA records show no health-based violations for Rialto, City of since 2016.

Nearby cities

All 515 cities in California

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