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Flagstone Water Plant

What EPA’s and Texas’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
876 people
Connections
292
Water source
Groundwater
Based in
Magnolia, TX
County
Harris
Owner
Private
The ZIP code it serves

77338

The short answer

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

What handles it

What was found

Arsenic, uranium, fluoride, nitrate, chromium (total), haloacetic acids (HAA5) and total trihalomethanes (TTHM): Texas’s own results, samples taken from Feb. 22, 2023 to Aug. 24, 2026.

Above the health goal2

Arsenic

Comes from the source

Above the health goal

3.0ppb

Highest yearly average, 2023

Averaged by year, the highest was 3.0 ppb, in 2023: below EPA’s legal limit of 10 ppb, but above its health goal of zero. That is the only year on file.

What handles it

  • NSF/ANSI 58 look for “Arsenic (Pentavalent)<=50 ppb Reduction”
  • NSF/ANSI 53 look for “Arsenic (Pentavalent)<=50 ppb Reduction”

Uranium

Comes from the source

Above the health goal

1.6ppb

Highest yearly average, 2023

Averaged by year, the highest was 1.6 ppb, in 2023: below EPA’s legal limit of 30 ppb, but above its health goal of zero. That is the only year on file.

What handles it

Below EPA’s limits2

Fluoride

Forms or is added in treatment

Below EPA’s limits

0.14ppm

Highest yearly average, 2023

Averaged by year, the highest was 0.14 ppm, in 2023, below EPA’s legal limit of 4.0 ppm. That is the only year on file.

What handles it

Nitrate

Comes from the source

Below EPA’s limits

0.15ppm

Highest sample; found in 2 of 3

2025: not found

The highest sample, in 2024, was 0.15 ppm, below EPA’s legal limit of 10 ppm. In 2025, the latest year on file, it wasn’t found in its one sample.

What handles it

  • NSF/ANSI 58 look for “Nitrate/Nitrite Reduction”
  • NSF/ANSI 53 look for “Nitrate/Nitrite (30 ppm challenge)”
4 compounds tested and not foundBelow the reporting level in every sample. Not found is not the same as zero.
  • Chromium (total)
  • Haloacetic acids (HAA5)
  • Lead
  • Total trihalomethanes (TTHM)

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: Arsenic (Pentavalent)<=50 ppb Reduction

    For: Arsenic

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

  • NSF/ANSI 58

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

    For: Arsenic, Uranium

    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

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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. Arsenic, uranium, fluoride, nitrate, chromium (total), haloacetic acids (HAA5) and total trihalomethanes (TTHM) results here are Texas’s own from 2023 on, with EPA’s national file for 2012 to 2019. Flagstone Water Plant’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; Texas’s results run from Feb. 22, 2023 to Aug. 24, 2026.

Testing your own tap

Flagstone Water Plant’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 Texas certifies.

The 3 labs Texas certifies closest to the area Flagstone Water Plant serves, in a straight line. Call first: certification is test by test, and not every lab takes samples from homeowners.

  • Water Utility Services, Inc.

    Spring, TX · about 11 miles

    Certified for bacteria

    (281) 290-0704

  • A & B Environmental Services, Inc.

    Houston, TX · about 17 miles

    Certified for bacteria, lead and copper

    (713) 453-6060

  • Eurofins EMLab P&K – Houston

    Houston, TX · about 20 miles

    Certified for bacteria

    (281) 940-2580

Texas Well Owner Network, Texas A&M AgriLife Extension: Well Informed screening events, where well owners bring in water samples to be screened for common contaminants, followed by an hour-long session explaining the results. Upcoming events are on the network's calendar. Trainings, Texas Well Owner Network.

All 80 certified labs for Texas

Sources

PWSID TX1013708. Rebuilt from EPA data on Oct. 18, 2026.

Also in Harris County

All Texas utilities

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