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Cal American WC - Las Posas Estates

What EPA’s and California’s records show in this utility’s water: nitrate, arsenic and other regulated chemicals; lead and copper; and violations since 2016, with the certification that handles each result.

Serves
2,043 people
Connections
620
Water source
Surface water bought from another system
Based in
Rosemead, CA
County
Ventura
Owner
Private
The ZIP code it serves

93010

The short answer

1 result is above the health goal. The worst: Lead, above the health goal. No health-based violations on file since 2016.

What handles it

What was found

Lead and copper: EPA SDWIS monitoring periods ending 2005 to 2024.

Total trihalomethanes (TTHM) and haloacetic acids (HAA5): California’s own results, samples taken from Aug. 9, 2021 to Aug. 12, 2025, with EPA’s 2012 to 2019 file for earlier years.

Above the health goal1

Lead

Comes from pipes, often your own

Above the health goal

1.0ppb

90th percentile, 2022 to 2024

In the latest period, 9 in 10 homes sampled were at or below 1.0 ppb, below EPA’s action level of 15 ppb. The action level drops to 10 ppb on Nov. 1, 2027. EPA’s health goal for lead is zero.

What handles it

Below EPA’s limits2

Total trihalomethanes (TTHM)

Forms or is added in treatment

Below EPA’s limits

43.6ppb

Highest yearly average, 2021 to 2025

2025, one sample: 27.9 ppb

Averaged by year, the highest was 43.6 ppb, in 2023, below EPA’s legal limit of 80 ppb. In 2025, the latest year on file, its one sample was 27.9 ppb. Earlier, from 2012 to 2019, EPA’s file shows a highest yearly average of 27.6 ppb, in 2014.

What handles it

  • NSF/ANSI 53 look for “Trihalomethanes (TTHM) Reduction”
  • NSF/ANSI 58 look for “Trihalomethanes (TTHM) Reduction”

Haloacetic acids (HAA5)

Forms or is added in treatment

Below EPA’s limits

14.1ppb

Highest yearly average, 2021 to 2025

2025, one sample: 6.7 ppb

Averaged by year, the highest was 14.1 ppb, in 2023, below EPA’s legal limit of 60 ppb. In 2025, the latest year on file, its one sample was 6.7 ppb. Earlier, from 2012 to 2019, EPA’s file shows a highest yearly average of 7.9 ppb, in 2017.

What handles it

No certification claim covers this compound yet.

What handles it

A certification covers specific claims, not a whole standard. Look for these claims on the certifier’s listing, not the box. Wording varies a little: NSF writes “Lead Reduction,” WQA just “Lead.”

At the tap, or for the whole house?

Lead and copper usually come from pipes and fixtures inside or near your home. A whole-house system sits where water enters, so it cannot catch what your own plumbing adds after it. For those, the filter that counts is the one at the tap. How whole-house systems compare.

Filters with those claims on a certifier’s listing

Disclosure: TapBuff earns a commission if you buy through some links on this page. It does not change which standard or filter we name. As an Amazon Associate, TapBuff earns from qualifying purchases. How TapBuff makes money

Compare five-year costs

The best water filters for lead, ranked

Violations since 2016

No health-based violations on file with EPA since 2016.

What this report can’t tell you

  • Everything else. Total trihalomethanes (TTHM) and haloacetic acids (HAA5) results here are California’s own from 2021 on, with EPA’s national file for 2012 to 2019. Cal American WC - Las Posas Estates’s own annual report, which it must send you every year, has the contaminants this page does not show.

  • Your own plumbing. Lead results are the 90th percentile across homes the utility samples. Your home’s service line, solder and fixtures decide yours. A certified lab test is the only way to know.

  • What it means for your health. This page reports what the records show and EPA’s limits and goals; it is not medical advice. If you are worried about a health effect, talk to a doctor or your local health department.

  • Anything after the latest data. SDWIS data is from 2026 Q3; UCMR 5 didn’t sample this utility; California’s results run from Aug. 9, 2021 to Aug. 12, 2025.

Testing your own tap

Cal American WC - Las Posas Estates’s results are for the water it sends out. What your own service line, solder and fixtures add shows up only in a test of your tap, by a lab California certifies.

The 3 labs California certifies closest to the area Cal American WC - Las Posas Estates serves, in a straight line. Call first: certification is test by test, and not every lab takes samples from homeowners.

  • Ventura County Public Health Laboratory

    Oxnard, CA · about 4 miles

    Certified for bacteria

    (805) 981-5131

  • Camrosa Water District Wastewater Laboratory

    Camarillo, CA · about 5 miles

    Certified for bacteria

    (805) 248-0402

  • Fruit Growers Laboratory, Inc.

    Santa Paula, CA · about 7 miles

    Certified for bacteria, nitrate, lead and copper, metals, minerals and other inorganics, organic chemicals, disinfection byproducts, radioactivity

    (805) 392-2000

All 145 certified labs for California

Sources

PWSID CA5610081. Rebuilt from EPA data on Oct. 18, 2026.

Towns it serves

Also in Ventura County

All California utilities

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