How hard is the water in Fairfield, CA?

Tap water hardness
109mg/L
6.4gpg
Moderately hardReports range 109–148

Reported by City of Fairfield · July 2025

CA typical
121 mg/L
EPA health violations since 2016
1
Softener for 3 people
24k grain
Data
Utility report

The water in Fairfield carries roughly 109 mg/L of dissolved calcium and magnesium, or 6.4 grains per gallon. That is moderately hard water. The number comes from City of Fairfield, dated July 2025. Reports for this system disagree, with values from 109 to 148 mg/L.

Fairfield on the hardness scale, with nearby cities
060120180240300360+CA typical 121Napa: 54 mg/LNapa 54Benicia: 56 mg/LBenicia 56American Canyon: 65 mg/LAmerican Canyon 65Vallejo: 82 mg/LVallejo 82Pittsburg: 82 mg/LPittsburg 82Martinez: 84 mg/LMartinez 84Bay Point: 88 mg/LBay Point 88Vacaville: 94 mg/LVacaville 94Suisun City: 107 mg/LSuisun City 107Dixon: 152 mg/LDixon 152Fairfield 109mg/L as calcium carbonate060120180240300360+CA 121Napa: 54 mg/LNapa 54Benicia: 56 mg/LBenicia 56American Canyon: 65 mg/LAmerican C. 65Bay Point: 88 mg/LBay Point 88Vacaville: 94 mg/LVacaville 94Suisun City: 107 mg/LSuisun City 107109 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 109 mg/L, Fairfield is 12 mg/L below the typical California figure of 121. Of the 10 nearest cities we track, 9 have softer water and 1 has harder. The range nearby runs from 54 mg/L in Napa to 152 in Dixon.

What 109 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 Fairfield

3 people × 75 gallons a day × 6.4 gpg = 1,433 grains a day. A 24,000-grain unit regenerates about every 16 days.

Size it for your household

EPA record for Fairfield's water system

City of Fairfield · PWSID CA4810003

1 health-based violation since 2016

Serves about 120,720 people from surface water.

Health-based
1
Monitoring or reporting
1
Open now
2
20162017201820192020202120222023202420252026Lead and Copper Rule'16'18'20'22'24'26Lead and Copper Rule
Each dot is one health-based violation, placed at the start of its compliance period.
Contaminant or ruleViolationsPeriodStatus
Lead and Copper Rulecorrosion control and lead sampling120241 open

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 Fairfield water hard?

Somewhat. It measures about 109 mg/L (6.4 grains per gallon), which the USGS classes as moderately hard.

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

About 6.4 gpg. One grain per gallon equals 17.1 mg/L, so 109 mg/L divided by 17.1 gives 6.4.

What size water softener do I need in Fairfield?

For 3 people using 75 gallons each per day, 6.4 gpg works out to about 1,433 grains a day. A 24,000-grain softener covers that with a regeneration about every 16 days.

Has the Fairfield water system had EPA violations?

EPA records show 1 health-based violation for City of Fairfield since 2016, involving Lead and Copper Rule. 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 30, 2025), CC BY 4.0. Population: US Census Bureau. Violations: EPA ECHO. How we use them.