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Thunderbird CWD

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
1,056 people
Connections
320
Water source
Groundwater
Based in
Apple Valley, CA
County
San Bernardino
Owner
Local government
Hardness
Varies by source
The ZIP code it serves

92307

The short answer

1 result is above EPA’s legal limit, and 2 more are above the health goal. The worst: Nitrate, above the legal limit. 1 health-based violation since 2016.

What handles it

What was found

Nitrate, arsenic, uranium, fluoride, chromium (total), haloacetic acids (HAA5) and total trihalomethanes (TTHM): California’s own results, samples taken from Jan. 13, 2020 to July 13, 2026, with EPA’s 2012 to 2019 file for earlier years.

Above the legal limit1

Nitrate

Comes from the source

Above the legal limit

11ppm

Highest sample; found in 57 of 57

2026 average: 8.3 ppm

From 2025 to 2026, four samples were above EPA’s legal limit of 10 ppm, the highest 11 ppm in 2025. The next sample at the same point, within 30 days, kept the average above the limit every time. In 2026, the latest year on file, its 21 samples averaged 8.3 ppm. EPA recorded a violation for nitrate at this utility in 2025. Earlier, from 2012 to 2019, EPA’s file shows a highest sample of 9.3 ppm, in 2015.

What handles it

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

Above the health goal2

Arsenic

Comes from the source

Above the health goal

3.6ppb

Highest yearly average, 2020 to 2026

Averaged by year, the highest was 3.6 ppb, in 2026: below EPA’s legal limit of 10 ppb, but above its health goal of zero. That was also the latest year on file. Earlier, from 2012 to 2019, EPA’s file shows a highest yearly average of 3.0 ppb, in 2016.

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

2.8ppb

Highest yearly average, 2022

Averaged by year, the highest was 2.8 ppb, in 2022: below EPA’s legal limit of 30 ppb, but above its health goal of zero. Its highest single sample was 2.8 ppb. That is the only year on file.

What handles it

Below EPA’s limits4

Fluoride

Forms or is added in treatment

Below EPA’s limits

1.9ppm

Highest yearly average, 2020 to 2026

2026 average: 1.8 ppm

Averaged by year, the highest was 1.9 ppm, in 2021, below EPA’s legal limit of 4.0 ppm. Its highest single sample was 2.3 ppm. In 2026, the latest year on file, its 25 samples averaged 1.8 ppm. Earlier, from 2012 to 2019, EPA’s file shows a highest yearly average of 2.0 ppm, in 2012.

What handles it

Chromium (total)

Comes from the source

Below EPA’s limits

19ppb

Highest yearly average, 2020 to 2026

2026: not found

Averaged by year, the highest was 19 ppb, in 2023, below EPA’s legal limit of 100 ppb. In 2026, the latest year on file, it wasn’t found in its one sample.

What handles it

Haloacetic acids (HAA5)

Forms or is added in treatment

Below EPA’s limits

1.7ppb

Highest yearly average, 2020 to 2024

2024 average: 1.4 ppb

Averaged by year, the highest was 1.7 ppb, in 2020, below EPA’s legal limit of 60 ppb. Its highest single sample was 3.4 ppb. In 2024, the latest year on file, its two samples averaged 1.4 ppb.

What handles it

No certification claim covers this compound yet.

Total trihalomethanes (TTHM)

Forms or is added in treatment

Below EPA’s limits

1.1ppb

Highest yearly average, 2020 to 2026

2026: not found

Averaged by year, the highest was 1.1 ppb, in 2020, below EPA’s legal limit of 80 ppb. Its highest single sample was 4.3 ppb. In 2026, the latest year on file, it wasn’t found in its one sample. Earlier, from 2012 to 2019, EPA’s file shows a highest yearly average of 0.8 ppb, in 2016.

What handles it

  • NSF/ANSI 53 look for “Trihalomethanes (TTHM) Reduction”
  • NSF/ANSI 58 look for “Trihalomethanes (TTHM) Reduction”
One compound tested and not foundBelow the reporting level in every sample. Not found is not the same as zero.
  • 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: Nitrate/Nitrite (30 ppm challenge), Arsenic (Pentavalent)<=50 ppb Reduction

    For: Nitrate, Arsenic

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

  • NSF/ANSI 58

    Claims: Nitrate/Nitrite Reduction, Arsenic (Pentavalent)<=50 ppb Reduction, Uranium

    For: Nitrate, Arsenic, Uranium

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

At the tap, or for the whole house?

These come with the water itself, so a whole-house system certified for the same claims treats every tap and shower. A filter at the tap treats drinking water for much less. 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

Hard to very hard depending on the source, 160 to 260 mg/L (9.4 to 15.2 grains per gallon), across 2 sampling points, 2020 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, salt includedSoftener or salt-free conditioner?California water hardness, utility by utility

Violations since 2016

Contaminant or ruleTypePeriodMeasuredStatus
NitrateA sample was above the legal limit, for a contaminant judged one sample at a time.EPA: Maximum Contaminant Level Violation, Single SampleJan. 1, 2025 to Dec. 31, 202511 MG/LArchived
Health-based violations only. Resolved and archived mean the utility returned to compliance or the state closed the record. 2 monitoring or reporting violations not shown.

What this report can’t tell you

  • Everything else. Nitrate, arsenic, uranium, fluoride, chromium (total), haloacetic acids (HAA5) and total trihalomethanes (TTHM) results here are California’s own from 2020 on, with EPA’s national file for 2012 to 2019. Thunderbird CWD’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. 13, 2020 to July 13, 2026.

Testing your own tap

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

  • Geo-Monitor, Inc

    Hesperia, CA · about 12 miles

    Certified for bacteria

    (760) 244-3481

  • BSK Associates - San Bernardino Analytical Laboratory

    San Bernardino, CA · about 36 miles

    Certified for bacteria

    (559) 497-2888

  • Clinical Laboratory of San Bernardino, Inc.

    Grand Terrace, CA · about 39 miles

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

    (909) 825-7693

All 145 certified labs for California

Sources

PWSID CA3600306. Rebuilt from EPA data on Oct. 18, 2026.

Towns it serves

Also in San Bernardino County

All California utilities

What to do next