How hard is the water in Gilroy, CA?

Tap water hardness
113mg/L
6.6gpg
Moderately hard

Reported by City of Gilroy · October 2025

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

The water in Gilroy carries roughly 113 mg/L of dissolved calcium and magnesium, or 6.6 grains per gallon. That is moderately hard water. The number comes from City of Gilroy, dated October 2025.

Gilroy on the hardness scale, with nearby cities
060120180240300360+CA typical 121Morgan Hill: 49 mg/LMorgan Hill 49Rio del Mar: 98 mg/LRio del Mar 98Aptos: 98 mg/LAptos 98Salinas: 106 mg/LSalinas 106Soquel: 132 mg/LSoquel 132Capitola: 132 mg/LCapitola 132Pleasure Point: 132 mg/LPleasure Point 132Live Oak: 147 mg/LLive Oak 147Interlaken: 215 mg/LInterlaken 215Watsonville: 215 mg/LWatsonville 215Gilroy 113mg/L as calcium carbonate060120180240300360+CA 121Morgan Hill: 49 mg/LMorgan Hill 49Rio del Mar: 98 mg/LRio del Mar 98Aptos: 98 mg/LAptos 98Soquel: 132 mg/LSoquel 132Interlaken: 215 mg/LInterlaken 215Watsonville: 215 mg/LWatsonville 215113 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 113 mg/L, Gilroy is close to the typical California figure of 121 mg/L. Of the 10 nearest cities we track, 4 have softer water and 6 have harder. The range nearby runs from 49 mg/L in Morgan Hill to 215 in Interlaken.

What 113 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 Gilroy

3 people × 75 gallons a day × 6.6 gpg = 1,487 grains a day. A 24,000-grain unit regenerates about every 16 days.

Size it for your household

EPA record for Gilroy's water system

City of Gilroy · PWSID CA4310004

1 health-based violation since 2016

Serves about 59,426 people from groundwater.

Health-based
1
Monitoring or reporting
0
Open now
0
20162017201820192020202120222023202420252026Nitrate'16'18'20'22'24'26Nitrate
Each dot is one health-based violation, placed at the start of its compliance period.
Contaminant or ruleViolationsPeriodStatus
Nitrateoften from fertilizer or septic systems12022Resolved

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 Gilroy water hard?

Somewhat. It measures about 113 mg/L (6.6 grains per gallon), which the USGS classes as moderately hard.

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

About 6.6 gpg. One grain per gallon equals 17.1 mg/L, so 113 mg/L divided by 17.1 gives 6.6.

What size water softener do I need in Gilroy?

For 3 people using 75 gallons each per day, 6.6 gpg works out to about 1,487 grains a day. A 24,000-grain softener covers that with a regeneration about every 16 days.

Has the Gilroy water system had EPA violations?

EPA records show 1 health-based violation for City of Gilroy since 2016, involving Nitrate.

Nearby cities

All 515 cities in California

Hardness data: TapWaterData US Water Hardness (utility report, October 7, 2025), CC BY 4.0. Population: US Census Bureau. Violations: EPA ECHO. How we use them.