How hard is the water in Thousand Oaks, CA?

Tap water hardness
117mg/L
6.8gpg
Moderately hard

Reported by Cal American Water CO · October 2025

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

Thousand Oaks water measures 117 mg/L (6.8 gpg) of hardness, moderately hard by USGS standards. The number comes from Cal American Water CO, dated October 2025.

Thousand Oaks on the hardness scale, with nearby cities
060120180240300360+CA typical 121Calabasas: 77 mg/LCalabasas 77Fillmore: 77 mg/LFillmore 77Westlake Village: 88 mg/LWestlake Village 88Agoura Hills: 88 mg/LAgoura Hills 88Oak Park: 138 mg/LOak Park 138Simi Valley: 181 mg/LSimi Valley 181Moorpark: 190 mg/LMoorpark 190Camarillo: 218 mg/LCamarillo 218El Rio: 278 mg/LEl Rio 278Santa Paula: 383 mg/LSanta Paula 383Thousand Oaks 117mg/L as calcium carbonate060120180240300360+CA 121Westlake Village: 88 mg/LWestlake V. 88Agoura Hills: 88 mg/LAgoura Hil. 88Oak Park: 138 mg/LOak Park 138Simi Valley: 181 mg/LSimi Valley 181Moorpark: 190 mg/LMoorpark 190Camarillo: 218 mg/LCamarillo 218117 mg/Lmg/L as calcium carbonate
Soft 0–60 mg/LModerately hard 61–120 mg/LHard 121–180 mg/LVery hard 181+ mg/L

Thousand Oaks sits 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 77 mg/L in Calabasas to 383 in Santa Paula.

What 117 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 Thousand Oaks

3 people × 75 gallons a day × 6.8 gpg = 1,537 grains a day. A 24,000-grain unit regenerates about every 15 days.

Size it for your household

EPA record for Thousand Oaks's water system

City of Thousand Oaks Water Department · PWSID CA5610020

No health-based violations since 2016

Serves about 54,770 people from surface water.

Health-based
0
Monitoring or reporting
0
Open now
0

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

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 Thousand Oaks water hard?

Somewhat. It measures about 117 mg/L (6.8 grains per gallon), which the USGS classes as moderately hard.

What is the water hardness in Thousand Oaks in grains per gallon?

About 6.8 gpg. One grain per gallon equals 17.1 mg/L, so 117 mg/L divided by 17.1 gives 6.8.

What size water softener do I need in Thousand Oaks?

For 3 people using 75 gallons each per day, 6.8 gpg works out to about 1,537 grains a day. A 24,000-grain softener covers that with a regeneration about every 15 days.

Has the Thousand Oaks water system had EPA violations?

EPA records show no health-based violations for City of Thousand Oaks Water Department since 2016.

Nearby cities

All 515 cities in California

Hardness data: TapWaterData US Water Hardness (utility report, October 6, 2025), CC BY 4.0. Population: US Census Bureau. Violations: EPA ECHO. How we use them.