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Cws Southlake System

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
1,015 people
Connections
796
Water source
Groundwater
Based in
San Jose, CA
County
Kern
Owner
Private
Hardness
Very hard
The ZIP code it serves

93240

The short answer

1 result is above EPA’s legal limit, and 2 more are above the health goal. The worst: Copper, above the action level. No health-based violations on file since 2016.

What handles it

What was found

Lead and copper: EPA SDWIS monitoring periods ending 2016 to 2022.

Arsenic, uranium, nitrate, fluoride, chromium (total), total trihalomethanes (TTHM) and haloacetic acids (HAA5): California’s own results, samples taken from Jan. 22, 2020 to June 22, 2026, with EPA’s 2012 to 2019 file for earlier years.

Above the legal limit1

Copper

Comes from pipes, often your own

Above the action level

1.5ppm

90th percentile, 2022

In the latest period, 9 in 10 homes sampled were at or below 1.5 ppm, above EPA’s action level of 1.3 ppm.

What handles it

Above the health goal2

Arsenic

Comes from the source

Above the health goal

4.6ppb

Highest yearly average, 2020 to 2026

2026 average: 4.3 ppb

Averaged by year, the highest was 4.6 ppb, in 2022: below EPA’s legal limit of 10 ppb, but above its health goal of zero. Its highest single sample was 6.8 ppb. In 2026, the latest year on file, its six samples averaged 4.3 ppb. Earlier, from 2012 to 2019, EPA’s file shows a highest yearly average of 4.6 ppb, in 2018.

What handles it

  • NSF/ANSI 58 look for “Arsenic (Pentavalent)<=50 ppb Reduction”
  • NSF/ANSI 53 look for “Arsenic (Pentavalent)<=50 ppb Reduction”

Uranium

Comes from the source

Above the health goal

12.8ppb

Highest yearly average, 2020 to 2026

2026 average: 11.8 ppb

Averaged by year, the highest was 12.8 ppb, in 2024: below EPA’s legal limit of 30 ppb, but above its health goal of zero. Its highest single sample was 26.8 ppb. In 2026, the latest year on file, its eight samples averaged 11.8 ppb. Earlier, from 2012 to 2019, EPA’s file shows a highest yearly average of 13.9 ppb, in 2012.

What handles it

Below EPA’s limits4

Nitrate

Comes from the source

Below EPA’s limits

7.9ppm

Highest sample; found in 158 of 158

2026 average: 5.5 ppm

The highest sample, in 2022, was 7.9 ppm, below EPA’s legal limit of 10 ppm. In 2026, the latest year on file, its 31 samples averaged 5.5 ppm. Earlier, from 2012 to 2019, EPA’s file shows a highest sample of 7.0 ppm, in 2014.

What handles it

  • NSF/ANSI 58 look for “Nitrate/Nitrite Reduction”
  • NSF/ANSI 53 look for “Nitrate/Nitrite (30 ppm challenge)”

Fluoride

Forms or is added in treatment

Below EPA’s limits

0.37ppm

Highest yearly average, 2020 to 2026

2026 average: 0.32 ppm

Averaged by year, the highest was 0.37 ppm, in 2021, below EPA’s legal limit of 4.0 ppm. Its highest single sample was 0.5 ppm. In 2026, the latest year on file, its 31 samples averaged 0.32 ppm. Earlier, from 2012 to 2019, EPA’s file shows a highest yearly average of 0.41 ppm, in 2012.

What handles it

Chromium (total)

Comes from the source

Below EPA’s limits

7.7ppb

Highest yearly average, 2020 to 2026

2026: not found

Averaged by year, the highest was 7.7 ppb, in 2022, below EPA’s legal limit of 100 ppb. Its highest single sample was 10.5 ppb. In 2026, the latest year on file, it wasn’t found in any of its two samples. Earlier, from 2012 to 2019, EPA’s file shows a highest yearly average of 8.8 ppb, in 2016.

What handles it

Total trihalomethanes (TTHM)

Forms or is added in treatment

Below EPA’s limits

4.2ppb

Highest yearly average, 2020 to 2026

2026: not found

Averaged by year, the highest was 4.2 ppb, in 2025, below EPA’s legal limit of 80 ppb. Its highest single sample was 8.4 ppb. In 2026, the latest year on file, it wasn’t found in any of its two samples. Earlier, from 2012 to 2019, EPA’s file shows a highest yearly average of 2.7 ppb, in 2019.

What handles it

  • NSF/ANSI 53 look for “Trihalomethanes (TTHM) Reduction”
  • NSF/ANSI 58 look for “Trihalomethanes (TTHM) Reduction”
2 compounds tested and not foundBelow the reporting level in every sample. Not found is not the same as zero.
  • Haloacetic acids (HAA5)
  • Lead

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.”

  • NSF/ANSI 53

    Claims: Copper Reduction, Arsenic (Pentavalent)<=50 ppb Reduction

    For: Copper, Arsenic

    Other certifiers’ wording: Arsenic (III) (50 ppb influent level)

  • NSF/ANSI 58

    Claims: Copper Reduction, Arsenic (Pentavalent)<=50 ppb Reduction, Uranium

    For: Copper, Arsenic, Uranium

    Other certifiers’ wording: Arsenic (Pentavalent)<=300 ppb Reduction; Arsenic (V) (300 ppb influent level)

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 reverse osmosis systems, ranked

Hardness

Very hard, typically 252 mg/L (14.7 grains per gallon), across 5 sampling points, 2019 to 2026.

Hardness is calcium and magnesium. EPA sets no limit for it: it shows up as scale on fixtures and in water heaters, and as soap that won’t lather. USGS calls water above 60 mg/L moderately hard, above 120 hard and above 180 very hard.

Softeners compared at 14.7 grains per gallon, salt includedSoftener or salt-free conditioner?California water hardness, utility by utility

Violations since 2016

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

What this report can’t tell you

  • Everything else. Arsenic, uranium, nitrate, fluoride, chromium (total), total trihalomethanes (TTHM) and haloacetic acids (HAA5) results here are California’s own from 2020 on, with EPA’s national file for 2012 to 2019. Cws Southlake System’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 Jan. 22, 2020 to June 22, 2026.

Testing your own tap

Cws Southlake System’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 Cws Southlake System serves, in a straight line. Call first: certification is test by test, and not every lab takes samples from homeowners.

  • Pace Analytical Services, LLC dba BC Laboratories, Inc.

    Bakersfield, CA · about 37 miles

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

    (661) 327-4911

  • Zalco Laboratories, Inc.

    Bakersfield, CA · about 37 miles

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

    (661) 395-0539

  • BSK Associates - Bakersfield Analytical Laboratory

    Bakersfield, CA · about 42 miles

    Certified for bacteria

    (661) 327-0671

All 145 certified labs for California

Sources

PWSID CA1510039. Rebuilt from EPA data on Oct. 18, 2026.

Towns it serves

Also in Kern County

All California utilities

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