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Nacimiento 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
2,191 people
Connections
664
Water source
Surface water
Based in
Bradley, CA
County
San Luis Obispo
Owner
Private
Hardness
Hard
The ZIP code it serves

93426

The short answer

2 results are above EPA’s legal limit, and 1 more is above the health goal. The worst: Haloacetic acids (HAA5), above the legal limit. 25 health-based violations since 2016.

What handles it

What was found

Haloacetic acids (HAA5), total trihalomethanes (TTHM), arsenic, fluoride, chromium (total) and nitrate: California’s own results, samples taken from April 15, 2020 to June 9, 2026, with EPA’s 2012 to 2019 file for earlier years.

Above the legal limit2

Haloacetic acids (HAA5)

Forms or is added in treatment

Above the legal limit

83.6ppb

Highest yearly average, 2020 to 2026

2026 average: 55 ppb

Averaged by year, the highest was 83.6 ppb, in 2022, above EPA’s legal limit of 60 ppb. Its highest single sample was 180 ppb. In 2026, the latest year on file, its four samples averaged 55 ppb. EPA recorded violations for haloacetic acids (HAA5) at this utility in 2020, 2022, 2023 and 2024. Earlier, from 2012 to 2019, EPA’s file shows a highest yearly average of 72.9 ppb, in 2018, and EPA recorded violations in 2012, 2015, 2016, 2018 and 2019.

What handles it

No certification claim covers this compound yet.

Total trihalomethanes (TTHM)

Forms or is added in treatment

Above the legal limit

83.2ppb

Highest yearly average, 2020 to 2026

2026 average: 41.9 ppb

Averaged by year, the highest was 83.2 ppb, in 2022, above EPA’s legal limit of 80 ppb. Its highest single sample was 184 ppb. In 2026, the latest year on file, its four samples averaged 41.9 ppb. EPA recorded violations for total trihalomethanes (TTHM) at this utility in 2022 and 2023. Earlier, from 2012 to 2019, EPA’s file shows a highest yearly average of 85.4 ppb, in 2016, and EPA recorded violations in 2016, 2017 and 2019.

What handles it

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

Above the health goal1

Arsenic

Comes from the source

Above the health goal

1.4ppb

Highest yearly average, 2020 to 2025

Averaged by year, the highest was 1.4 ppb, in 2025: 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 3.3 ppb, in 2015.

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 limits1

Fluoride

Forms or is added in treatment

Below EPA’s limits

0.18ppm

Highest yearly average, 2020 to 2025

2025, one sample: 0.14 ppm

Averaged by year, the highest was 0.18 ppm, in 2020, below EPA’s legal limit of 4.0 ppm. In 2025, the latest year on file, its one sample was 0.14 ppm. Earlier, from 2012 to 2019, EPA’s file shows a highest yearly average of 0.24 ppm, in 2018.

What handles it

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

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: Trihalomethanes (TTHM) Reduction, Arsenic (Pentavalent)<=50 ppb Reduction

    For: Total trihalomethanes (TTHM), Arsenic

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

  • NSF/ANSI 58

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

    For: Total trihalomethanes (TTHM), Arsenic

    Other certifiers’ wording: 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, typically 137 mg/L (8 grains per gallon), across 2 sampling points, 2019 to 2025.

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 8 grains per gallon, salt includedSoftener or salt-free conditioner?California water hardness, utility by utility

Violations since 2016

Contaminant or ruleTypePeriodMeasuredStatus
Total Haloacetic Acids (HAA5)The running average was above the legal limit.EPA: Maximum Contaminant Level Violation, AverageOct. 1, 2024 to Dec. 31, 20240.66 MG/LArchived
Total Haloacetic Acids (HAA5)The running average was above the legal limit.EPA: Maximum Contaminant Level Violation, AverageApril 1, 2023 to June 30, 20230.1 MG/LResolved
TTHMThe running average was above the legal limit.EPA: Maximum Contaminant Level Violation, AverageApril 1, 2023 to June 30, 20230.1 MG/LResolved
TTHMThe running average was above the legal limit.EPA: Maximum Contaminant Level Violation, AverageJan. 1, 2023 to March 31, 20230.1 MG/LResolved
Total Haloacetic Acids (HAA5)The running average was above the legal limit.EPA: Maximum Contaminant Level Violation, AverageJan. 1, 2023 to March 31, 20230.1 MG/LResolved
Total Haloacetic Acids (HAA5)The running average was above the legal limit.EPA: Maximum Contaminant Level Violation, AverageOct. 1, 2022 to Dec. 31, 20220.083 MG/LResolved
TTHMThe running average was above the legal limit.EPA: Maximum Contaminant Level Violation, AverageOct. 1, 2022 to Dec. 31, 20220.083 MG/LResolved
TTHMThe running average was above the legal limit.EPA: Maximum Contaminant Level Violation, AverageJuly 1, 2022 to Sept. 30, 20220.091 MG/LResolved
Total Haloacetic Acids (HAA5)The running average was above the legal limit.EPA: Maximum Contaminant Level Violation, AverageJuly 1, 2022 to Sept. 30, 20220.072 MG/LResolved
Total Haloacetic Acids (HAA5)The running average was above the legal limit.EPA: Maximum Contaminant Level Violation, AverageJuly 1, 2020 to Sept. 30, 20200.07 MG/LResolved
Total Haloacetic Acids (HAA5)The running average was above the legal limit.EPA: Maximum Contaminant Level Violation, AverageApril 1, 2019 to June 30, 20190.08 MG/LResolved
Total Haloacetic Acids (HAA5)The running average was above the legal limit.EPA: Maximum Contaminant Level Violation, AverageApril 1, 2019 to June 30, 20190.079 MG/LResolved
Total Haloacetic Acids (HAA5)The running average was above the legal limit.EPA: Maximum Contaminant Level Violation, AverageJan. 1, 2019 to March 31, 20190.085 MG/LResolved
Total Haloacetic Acids (HAA5)The running average was above the legal limit.EPA: Maximum Contaminant Level Violation, AverageJan. 1, 2019 to March 31, 20190.086 MG/LResolved
TTHMThe running average was above the legal limit.EPA: Maximum Contaminant Level Violation, AverageJan. 1, 2019 to March 31, 20190.081 MG/LResolved
TTHMThe running average was above the legal limit.EPA: Maximum Contaminant Level Violation, AverageJan. 1, 2019 to March 31, 20190.084 MG/LResolved
Total Haloacetic Acids (HAA5)The running average was above the legal limit.EPA: Maximum Contaminant Level Violation, AverageOct. 1, 2018 to Dec. 31, 20180.083 MG/LResolved
Total Haloacetic Acids (HAA5)The running average was above the legal limit.EPA: Maximum Contaminant Level Violation, AverageOct. 1, 2018 to Dec. 31, 20180.063 MG/LResolved
Total Haloacetic Acids (HAA5)The running average was above the legal limit.EPA: Maximum Contaminant Level Violation, AverageJuly 1, 2018 to Sept. 30, 20180.11 MG/LResolved
TTHMThe running average was above the legal limit.EPA: Maximum Contaminant Level Violation, AverageJan. 1, 2017 to March 31, 20170.087 MG/LResolved
TTHMThe running average was above the legal limit.EPA: Maximum Contaminant Level Violation, AverageOct. 1, 2016 to Dec. 31, 20160.092 MG/LResolved
Total Haloacetic Acids (HAA5)The running average was above the legal limit.EPA: Maximum Contaminant Level Violation, AverageJuly 1, 2016 to Sept. 30, 20160.073 MG/LResolved
TTHMThe running average was above the legal limit.EPA: Maximum Contaminant Level Violation, AverageJuly 1, 2016 to Sept. 30, 20160.099 MG/LResolved
TTHMThe running average was above the legal limit.EPA: Maximum Contaminant Level Violation, AverageApril 1, 2016 to June 30, 20160.088 MG/LResolved
TTHMThe running average was above the legal limit.EPA: Maximum Contaminant Level Violation, AverageJan. 1, 2016 to March 31, 20160.084 MG/LResolved
Health-based violations only. Resolved and archived mean the utility returned to compliance or the state closed the record. 13 monitoring or reporting violations not shown.

What this report can’t tell you

  • Everything else. Haloacetic acids (HAA5), total trihalomethanes (TTHM), arsenic, fluoride, chromium (total) and nitrate results here are California’s own from 2020 on, with EPA’s national file for 2012 to 2019. Nacimiento 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 April 15, 2020 to June 9, 2026.

Testing your own tap

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

  • County of San Luis Obispo Public Health Laboratory

    San Luis Obispo, CA · about 43 miles

    Certified for bacteria

    (805) 781-5507

  • Fruit Growers Laboratory, Inc.

    San Luis Obispo, CA · about 44 miles

    Certified for bacteria

    (805) 783-2940

  • Abalone Coast Analytical, Inc.

    San Luis Obispo, CA · about 45 miles

    Certified for bacteria

    (805) 595-1080

All 145 certified labs for California

Sources

PWSID CA4010027. Rebuilt from EPA data on Oct. 18, 2026.

Also in San Luis Obispo County

All California utilities

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