Skip to content

City water profile

Thousand Oaks water quality

Compare local ZIP estimates, evidence quality, associated public systems, and compliance history for Thousand Oaks, California.

Median indexed hardness

303PPM

4 indexed ZIPs

Range 303–403 PPM

State comparison
114 PPM above
State hardness rank
#25 of 242
Matched utilities
1
Active health records
0

City summary

What the indexed records say

Thousand Oaks has 4 published ZIP profiles across Ventura County. The indexed median is 303 PPM, compared with 189 PPM across California.

Among the 242 Californiacities with an indexed median, Thousand Oaks ranks #25from highest to lowest. Across all 678 state ZIP profiles, available estimates run from 3.3to 728.5 PPM.

The 303–403 PPM range shows how much the available ZIP estimates vary within the city label. At least one estimate is marked low confidence, so observation distance and date deserve extra attention.

Hardness distribution

How local ZIP estimates compare

Soft0 ZIPs
Moderately hard0 ZIPs
Hard0 ZIPs
Very hard4 ZIPs

4 of 4 ZIP profiles have a hardness estimate. Bars count ZIP profiles, not households or laboratory samples.

Evidence quality

Distance, dates, and confidence

Median nearest distance
45.8 miles
Profiles with evidence
4/4

Confidence labels

High: 0Moderate: 0Low: 4

Observation window: Jan 7, 2016 to May 14, 2026.

ZIP directory

Water reports in Thousand Oaks

Open a ZIP for site-level provenance and measurements.

ZIP code

91320

Very Hard

403 PPM

Nearest site
46.3 mi
Confidence
Low

View full ZIP evidence →

ZIP code

91360

Very Hard

303 PPM

Nearest site
41.4 mi
Confidence
Low

View full ZIP evidence →

ZIP code

91361

Very Hard

303 PPM

Nearest site
45.8 mi
Confidence
Low

View full ZIP evidence →

ZIP code

91362

Very Hard

303 PPM

Nearest site
40.6 mi
Confidence
Low

View full ZIP evidence →

Public water systems

Utilities associated with this city

City Of Thousand Oaks Water Department

PWSID CA5610020

Surface water
System population served
53,157
Last reported
Jun 22, 2026

A municipal system, in-state city, and served county all agree with this Census ZCTA.

Compliance history

What EPA records show

No active health-based violation appears among the associated systems in the represented EPA reporting quarter. This does not mean every contaminant was tested at every tap.

No violation records are included in the current lookback window.

Practical next steps

Move from index to evidence

  1. 1. Open your ZIP. Check distance, dates, confidence, and the associated utility.
  2. 2. Read the current CCR. Confirm source water, detections, limits, ranges, and notices.
  3. 3. Test the tap when needed. Confirm health concerns or treatment sizing with the right method.

Questions people ask

About water in Thousand Oaks

Is the water hard?

The indexed city median is 303 PPM. Open the ZIP report to verify the distance and confidence behind that estimate.

Is the tap water safe?

Compliance history is utility-wide and cannot guarantee conditions at every tap. Check current notices and test when address-specific evidence is needed.

Do I need treatment?

Choose treatment only after confirming the problem at the property. A softener targets hardness; contaminant treatment requires a matching, verified performance claim.