How hard is the water in Fontana, CA?

Tap water hardness
92mg/L
5.4gpg
Moderately hardReports range 55–114

Reported by San Gabriel Valley WC - Fontana · September 2025

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

Tap water in Fontana has about 92 mg/L of hardness, which is 5.4 grains per gallon. On the USGS scale that counts as moderately hard. The number comes from San Gabriel Valley WC - Fontana, dated September 2025. Reports for this system disagree, with values from 55 to 114 mg/L.

Fontana 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 79Rialto: 89 mg/LRialto 89Bloomington: 96 mg/LBloomington 96Highgrove: 99 mg/LHighgrove 99Ontario: 104 mg/LOntario 104Jurupa Valley: 122 mg/LJurupa Valley 122Grand Terrace: 137 mg/LGrand Terrace 137Colton: 139 mg/LColton 139Fontana 92mg/L as calcium carbonate060120180240300360+CA 121Rancho Cucamonga: 68 mg/LRancho Cuc. 68Muscoy: 72 mg/LMuscoy 72Rialto: 89 mg/LRialto 89Bloomington: 96 mg/LBloomington 96Jurupa Valley: 122 mg/LJurupa Val. 122Colton: 139 mg/LColton 13992 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 92 mg/L, Fontana is 29 mg/L below the typical California figure of 121. Of the 10 nearest cities we track, 4 have softer water and 6 have harder. The range nearby runs from 68 mg/L in Rancho Cucamonga to 139 in Colton.

What 92 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 Fontana

3 people × 75 gallons a day × 5.4 gpg = 1,210 grains a day. A 24,000-grain unit regenerates about every 19 days.

Size it for your household

EPA record for Fontana's water system

San Gabriel Valley WC - Fontana · PWSID CA3610041

No health-based violations since 2016

Serves about 228,270 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 Fontana water hard?

Somewhat. It measures about 92 mg/L (5.4 grains per gallon), which the USGS classes as moderately hard.

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

About 5.4 gpg. One grain per gallon equals 17.1 mg/L, so 92 mg/L divided by 17.1 gives 5.4.

What size water softener do I need in Fontana?

For 3 people using 75 gallons each per day, 5.4 gpg works out to about 1,210 grains a day. A 24,000-grain softener covers that with a regeneration about every 19 days.

Has the Fontana water system had EPA violations?

EPA records show no health-based violations for San Gabriel Valley WC - Fontana since 2016.

Nearby cities

All 515 cities in California

Hardness data: TapWaterData US Water Hardness (utility report, September 23, 2025), CC BY 4.0. Population: US Census Bureau. Violations: EPA ECHO. How we use them.