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Muller Mutual Water Company

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
154 people
Connections
55
Water source
Surface water bought from another system
Based in
Tuolumne, CA
County
Tuolumne
Owner
Private
The ZIP code it serves

95379

The short answer

Nothing in EPA’s and California’s records for this utility is above a health goal. That covers nitrate, arsenic and other regulated chemicals, plus lead and copper, not everything. No health-based violations on file since 2016.

What was found

Total trihalomethanes (TTHM) and haloacetic acids (HAA5): California’s own results, samples taken from Feb. 12, 2020 to June 30, 2026, with EPA’s 2012 to 2019 file for earlier years.

Below EPA’s limits2

Total trihalomethanes (TTHM)

Forms or is added in treatment

Below EPA’s limits

48.5ppb

Highest yearly average, 2020 to 2026

Averaged by year, the highest was 48.5 ppb, in 2026, below EPA’s legal limit of 80 ppb. Its highest single sample was 67.7 ppb. That was also the latest year on file. Earlier, from 2012 to 2019, EPA’s file shows a highest yearly average of 44.3 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

32.5ppb

Highest yearly average, 2020 to 2026

Averaged by year, the highest was 32.5 ppb, in 2026, below EPA’s legal limit of 60 ppb. Its highest single sample was 46 ppb. That was also the latest year on file. Earlier, from 2012 to 2019, EPA’s file shows a highest yearly average of 35.1 ppb, in 2016.

What handles it

No certification claim covers this compound yet.

One compound tested and not foundBelow the reporting level in every sample. Not found is not the same as zero.
  • Lead

Violations since 2016

No health-based violations on file with EPA since 2016. There is 1 monitoring or reporting violation: a sample missed, late or not reported.

What this report can’t tell you

  • Everything else. 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. Muller Mutual Water Company’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 Feb. 12, 2020 to June 30, 2026.

Testing your own tap

Muller Mutual Water Company’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 Muller Mutual Water Company serves, in a straight line. Call first: certification is test by test, and not every lab takes samples from homeowners.

  • Precision Enviro-Tech

    Twain Harte, CA · about 7 miles

    Certified for bacteria

    (209) 477-8105

  • 49er Water Laboratory

    Jackson, CA · about 43 miles

    Certified for bacteria, nitrate, minerals and other inorganics

    (530) 277-2770

  • Aemtek, Inc.

    Modesto, CA · about 47 miles

    Certified for bacteria

    (510) 979-1979

All 145 certified labs for California

Sources

PWSID CA5500064. Rebuilt from EPA data on Oct. 18, 2026.

Also in Tuolumne County

All California utilities

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