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Darwin Community Service District

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
25 people
Connections
63
Water source
Groundwater influenced by surface water
Based in
Darwin, CA
County
Inyo
Owner
Private
Hardness
Very hard
The ZIP code it serves

93522

The short answer

1 result is above EPA’s legal limit, and 1 more is above the health goal. The worst: Total trihalomethanes (TTHM), above the legal limit. 3 health-based violations since 2016.

What handles it

What was found

Total trihalomethanes (TTHM), uranium, haloacetic acids (HAA5), nitrate, fluoride, arsenic and chromium (total): California’s own results, samples taken from March 24, 2020 to June 19, 2026, with EPA’s 2012 to 2019 file for earlier years.

Above the legal limit1

Total trihalomethanes (TTHM)

Forms or is added in treatment

Above the legal limit

160ppb

Highest yearly average, 2020 to 2026

2026 average: 95 ppb

Averaged by year, the highest was 160 ppb, in 2020, about twice EPA’s legal limit of 80 ppb. Its highest single sample was 190 ppb. In 2026, the latest year on file, its two samples averaged 95 ppb, above the limit. EPA recorded a violation for total trihalomethanes (TTHM) at this utility in 2021. Earlier, from 2012 to 2019, EPA’s file shows a highest yearly average of 87 ppb, in 2019.

What handles it

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

Above the health goal1

Uranium

Comes from the source

Above the health goal

7.3ppb

Highest yearly average, 2025

Averaged by year, the highest was 7.3 ppb, in 2025: below EPA’s legal limit of 30 ppb, but above its health goal of zero. That is the only year on file. Earlier, from 2012 to 2019, EPA’s file shows a highest yearly average of 5.7 ppb, in 2016.

What handles it

Below EPA’s limits3

Haloacetic acids (HAA5)

Forms or is added in treatment

Below EPA’s limits

36.5ppb

Highest yearly average, 2020 to 2026

Averaged by year, the highest was 36.5 ppb, in 2026, below EPA’s legal limit of 60 ppb. Its highest single sample was 59 ppb. That was also the latest year on file. Earlier, from 2012 to 2019, EPA’s file shows a highest yearly average of 24 ppb, in 2019.

What handles it

No certification claim covers this compound yet.

Nitrate

Comes from the source

Below EPA’s limits

0.77ppm

Highest sample; found in 10 of 10

2026, one sample: 0.52 ppm

The highest sample, in 2021, was 0.77 ppm, below EPA’s legal limit of 10 ppm. In 2026, the latest year on file, its one sample was 0.52 ppm. Earlier, from 2012 to 2019, EPA’s file shows a highest sample of 0.77 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

0.28ppm

Highest yearly average, 2020 to 2026

2026, one sample: 0.22 ppm

Averaged by year, the highest was 0.28 ppm, in 2022, below EPA’s legal limit of 4.0 ppm. In 2026, the latest year on file, its one sample was 0.22 ppm. Earlier, from 2012 to 2019, EPA’s file shows a highest yearly average of 0.23 ppm, in 2019.

What handles it

3 compounds tested and not foundBelow the reporting level in every sample. Not found is not the same as zero.
  • Arsenic
  • Chromium (total)
  • 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

    Claim: Trihalomethanes (TTHM) Reduction

    For: Total trihalomethanes (TTHM)

    Other certifiers’ wording: VOC Reduction

  • NSF/ANSI 58

    Claims: Trihalomethanes (TTHM) Reduction, Uranium

    For: Total trihalomethanes (TTHM), Uranium

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

Hardness

Very hard, 300 mg/L (17.5 grains per gallon), at its one sampling point, 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 17.5 grains per gallon, salt includedSoftener or salt-free conditioner?California water hardness, utility by utility

Violations since 2016

Contaminant or ruleTypePeriodMeasuredStatus
TTHMThe running average was above the legal limit.EPA: Maximum Contaminant Level Violation, AverageApril 1, 2021 to June 30, 20210.087 MG/LResolved
TTHMThe running average was above the legal limit.EPA: Maximum Contaminant Level Violation, AverageJan. 1, 2021 to March 31, 20210.087 MG/LResolved
Surface Water Treatment RuleWater drawn from a river, lake or reservoir was not filtered as required.EPA: Failure to Filter (SWTR)Aug. 1, 2019—Resolved
Health-based violations only. Resolved and archived mean the utility returned to compliance or the state closed the record. 4 monitoring or reporting violations not shown.

What this report can’t tell you

  • Everything else. Total trihalomethanes (TTHM), uranium, haloacetic acids (HAA5), nitrate, fluoride, arsenic and chromium (total) results here are California’s own from 2020 on, with EPA’s national file for 2012 to 2019. Darwin Community Service District’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 March 24, 2020 to June 19, 2026.

Testing your own tap

Darwin Community Service District’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 lab California certifies closest to the area Darwin Community Service District serves, in a straight line. Call first: certification is test by test, and not every lab takes samples from homeowners.

  • Inyo County Water Lab

    Independence, CA · about 48 miles

    Certified for bacteria

    (760) 878-8476

All 145 certified labs for California

Sources

PWSID CA1400098. Rebuilt from EPA data on Oct. 18, 2026.

Also in Inyo County

All California utilities

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