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Preserve at Millerton Lake Water System

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
204 people
Connections
243
Water source
Groundwater
Based in
Pismo Beach, CA
County
Madera
Owner
Private
Hardness
Varies by source

The short answer

2 results are above the health goal. The worst: Nitrate, above the health goal. No health-based violations on file since 2016.

What handles it

What was found

Nitrate, arsenic, fluoride, total trihalomethanes (TTHM), haloacetic acids (HAA5), chromium (total) and uranium: California’s own results, samples taken from Aug. 28, 2020 to Jan. 14, 2026, with EPA’s 2012 to 2019 file for earlier years.

Above the health goal2

Nitrate

Comes from the source

Above the health goal

10.8ppm

Highest sample; found in 9 of 16

2026, one sample: 7.8 ppm

One sample, in 2024, was above EPA’s legal limit of 10 ppm, at 10.8 ppm. The next sample at the same point, within 30 days, brought the average back under the limit. 10 ppm is also EPA’s health goal. In 2026, the latest year on file, its one sample was 7.8 ppm. EPA recorded no violation for nitrate at this utility since 2020. Earlier, from 2012 to 2019, EPA’s file shows a highest sample of 1.7 ppm, in 2019.

What handles it

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

Arsenic

Comes from the source

Above the health goal

6.6ppb

Highest yearly average, 2020 to 2023

2023: not found

Averaged by year, the highest was 6.6 ppb, in 2020: below EPA’s legal limit of 10 ppb, but above its health goal of zero. In 2023, the latest year on file, it wasn’t found in any of its three samples. Earlier, from 2012 to 2019, EPA’s file shows a highest yearly average of 0.97 ppb, in 2019.

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

Fluoride

Forms or is added in treatment

Below EPA’s limits

0.65ppm

Highest yearly average, 2020 to 2023

2023 average: 0.37 ppm

Averaged by year, the highest was 0.65 ppm, in 2020, below EPA’s legal limit of 4.0 ppm. In 2023, the latest year on file, its three samples averaged 0.37 ppm. Earlier, from 2012 to 2019, EPA’s file shows a highest yearly average of 0.38 ppm, in 2019.

What handles it

Total trihalomethanes (TTHM)

Forms or is added in treatment

Below EPA’s limits

10.6ppb

Highest yearly average, 2020 to 2025

Averaged by year, the highest was 10.6 ppb, in 2025, below EPA’s legal limit of 80 ppb. Its highest single sample was 15 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”

Haloacetic acids (HAA5)

Forms or is added in treatment

Below EPA’s limits

3.2ppb

Highest yearly average, 2020 to 2025

2025, one sample: 1.1 ppb

Averaged by year, the highest was 3.2 ppb, in 2024, below EPA’s legal limit of 60 ppb. In 2025, the latest year on file, its one sample was 1.1 ppb.

What handles it

No certification claim covers this compound yet.

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

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

Soft to moderately hard depending on the source, 51 to 113 mg/L (3 to 6.6 grains per gallon), across 4 sampling points, 2019 to 2023.

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

No health-based violations on file with EPA since 2016.

What this report can’t tell you

  • Everything else. Nitrate, arsenic, fluoride, total trihalomethanes (TTHM), haloacetic acids (HAA5), chromium (total) and uranium results here are California’s own from 2020 on, with EPA’s national file for 2012 to 2019. Preserve at Millerton Lake Water System’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 Aug. 28, 2020 to Jan. 14, 2026.

Testing your own tap

Preserve at Millerton Lake Water System’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.

No lab California certifies is within 75 miles of the area Preserve at Millerton Lake Water System serves on the state’s list. Some take samples by mail; the state’s page lists them all.

All 145 certified labs for California

Sources

PWSID CA2010018. Rebuilt from EPA data on Oct. 18, 2026.

Also in Madera County

All California utilities

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