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Thimio MWC

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
59 people
Connections
21
Water source
Groundwater
Based in
Prunedale, CA
County
Monterey
Owner
Private
Hardness
Hard
The ZIP code it serves

95076

The short answer

1 result is above EPA’s legal limit, and 1 more is above the health goal. The worst: Nitrate, above the legal limit. 7 health-based violations since 2016.

What handles it

What was found

Nitrate, arsenic, total trihalomethanes (TTHM) and haloacetic acids (HAA5): California’s own results, samples taken from Jan. 8, 2020 to April 6, 2026, with EPA’s 2012 to 2019 file for earlier years.

Chromium (total) and fluoride: EPA’s compliance monitoring file, samples taken from Feb. 25, 2019 to Feb. 25, 2019. Newer results are in the utility’s annual water quality report.

Above the legal limit1

Nitrate

Comes from the source

Above the legal limit

12.4ppm

Highest sample; found in 27 of 27

2026 average: 11.3 ppm

From 2022 to 2026, 16 samples were above EPA’s legal limit of 10 ppm, the highest 12.4 ppm in 2025. The next sample at the same point, within 30 days, kept the average above the limit for two; 14 have no follow-up sample on file within 30 days. In 2026, the latest year on file, its two samples averaged 11.3 ppm, above the limit. EPA recorded violations for nitrate at this utility in 2022, 2023 and 2024. Earlier, from 2012 to 2019, EPA’s file shows a highest sample of 9.2 ppm, in 2019.

What handles it

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

Above the health goal1

Arsenic

Comes from the source

Above the health goal

1.1ppb

Highest yearly average, 2022 to 2025

2025: not found

Averaged by year, the highest was 1.1 ppb, in 2022: below EPA’s legal limit of 10 ppb, but above its health goal of zero. In 2025, 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 1.0 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”

Below EPA’s limits3

Chromium (total)

Comes from the source

Below EPA’s limits

14.5ppb

Highest yearly average, 2019

Averaged by year, the highest was 14.5 ppb, in 2019, below EPA’s legal limit of 100 ppb. That is the only year on file.

What handles it

Total trihalomethanes (TTHM)

Forms or is added in treatment

Below EPA’s limits

8.0ppb

Highest yearly average, 2020 to 2025

Averaged by year, the highest was 8.0 ppb, in 2025, below EPA’s legal limit of 80 ppb. That was also the latest year on file.

What handles it

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

Fluoride

Forms or is added in treatment

Below EPA’s limits

0.1ppm

Highest yearly average, 2019

Averaged by year, the highest was 0.1 ppm, in 2019, below EPA’s legal limit of 4.0 ppm. That is the only year on file.

What handles it

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: 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

    For: Nitrate, Arsenic

    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, 134 mg/L (7.8 grains per gallon), at its one sampling point, in 2019.

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 7.8 grains per gallon, 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 SampleApril 1, 2024 to June 30, 202411 MG/LArchived
NitrateA sample was above the legal limit, for a contaminant judged one sample at a time.EPA: Maximum Contaminant Level Violation, Single SampleJan. 1, 2024 to March 31, 202412 MG/LArchived
NitrateA sample was above the legal limit, for a contaminant judged one sample at a time.EPA: Maximum Contaminant Level Violation, Single SampleOct. 1, 2023 to Dec. 31, 202312 MG/LArchived
NitrateA sample was above the legal limit, for a contaminant judged one sample at a time.EPA: Maximum Contaminant Level Violation, Single SampleJan. 1, 2023 to March 31, 202311 MG/LArchived
NitrateA sample was above the legal limit, for a contaminant judged one sample at a time.EPA: Maximum Contaminant Level Violation, Single SampleOct. 1, 2022 to Dec. 31, 202211 MG/LArchived
NitrateA sample was above the legal limit, for a contaminant judged one sample at a time.EPA: Maximum Contaminant Level Violation, Single SampleJuly 1, 2022 to Sept. 30, 202211 MG/LArchived
NitrateThe running average was above the legal limit.EPA: Maximum Contaminant Level Violation, AverageApril 1, 2022 to June 30, 202211 MG/LArchived
Health-based violations only. Resolved and archived mean the utility returned to compliance or the state closed the record.

What this report can’t tell you

  • Everything else. Nitrate, arsenic, 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. Chromium (total) and fluoride come from EPA’s file alone, which ends in 2019. Thimio MWC’s own annual report, which it must send you every year, has newer results for those and 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. 8, 2020 to April 6, 2026; EPA’s compliance samples are from Feb. 25, 2019 to Feb. 25, 2019.

Testing your own tap

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

  • CM Analytical, Inc.

    Gilroy, CA · about 12 miles

    Certified for bacteria

    (408) 848-3619

  • Bracewell Engineering, Inc.

    Morgan Hill, CA · about 14 miles

    Certified for bacteria, nitrate, minerals and other inorganics

    (669) 258-5821

  • Santa Cruz County - Health Services Agency - Environmental Health

    Santa Cruz, CA · about 15 miles

    Certified for bacteria

    (831) 454-4624

All 145 certified labs for California

Sources

PWSID CA2702608. Rebuilt from EPA data on Oct. 18, 2026.

Also in Monterey County

All California utilities

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