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San Luis WSD

What EPA’s and Colorado’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
629 people
Connections
414
Water source
Groundwater
Based in
San Luis, CO
County
Costilla
Owner
Local government
The ZIP code it serves

81152

The short answer

1 result is above the health goal. The worst: Uranium, above the health goal. No health-based violations on file since 2016.

What handles it

What was found

Uranium, fluoride, nitrate, total trihalomethanes (TTHM), arsenic, chromium (total) and haloacetic acids (HAA5): Colorado’s own results, samples taken from Aug. 10, 2020 to Aug. 24, 2026, with EPA’s 2012 to 2019 file for earlier years.

Above the health goal1

Uranium

Comes from the source

Above the health goal

4.4ppb

Highest yearly average, 2025

Averaged by year, the highest was 4.4 ppb, in 2025: below EPA’s legal limit of 30 ppb, but above its health goal of zero. Its highest single sample was 5.5 ppb. That is the only year on file. Earlier, from 2012 to 2019, EPA’s file shows a highest yearly average of 6.2 ppb, in 2013.

What handles it

Below EPA’s limits3

Fluoride

Forms or is added in treatment

Below EPA’s limits

0.48ppm

Highest yearly average, 2022

Averaged by year, the highest was 0.48 ppm, in 2022, below EPA’s legal limit of 4.0 ppm. Its highest single sample was 0.51 ppm. That is the only year on file. Earlier, from 2012 to 2019, EPA’s file shows a highest yearly average of 0.5 ppm, in 2013.

What handles it

Nitrate

Comes from the source

Below EPA’s limits

0.4ppm

Highest sample; found in 10 of 10

2025 average: 0.31 ppm

The highest sample, in 2023, was 0.4 ppm, below EPA’s legal limit of 10 ppm. In 2025, the latest year on file, its two samples averaged 0.31 ppm. Earlier, from 2012 to 2019, EPA’s file shows a highest sample of 0.47 ppm, in 2013.

What handles it

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

Total trihalomethanes (TTHM)

Forms or is added in treatment

Below EPA’s limits

0.6ppb

Highest yearly average, 2020 to 2026

2026: not found

Averaged by year, the highest was 0.6 ppb, in 2020, below EPA’s legal limit of 80 ppb. In 2026, 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 2.0 ppb, in 2015.

What handles it

  • NSF/ANSI 53 look for “Trihalomethanes (TTHM) Reduction”
  • NSF/ANSI 58 look for “Trihalomethanes (TTHM) Reduction”
4 compounds tested and not foundBelow the reporting level in every sample. Not found is not the same as zero.
  • Arsenic
  • Chromium (total)
  • 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.”

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

None of the filters TapBuff has checked so far carry these claims. Search the certifier listings for the claim above.

Compare five-year costs

Violations since 2016

No health-based violations on file with EPA since 2016. There are 5 monitoring or reporting violations: a sample missed, late or not reported.

What this report can’t tell you

  • Everything else. Uranium, fluoride, nitrate, total trihalomethanes (TTHM), arsenic, chromium (total) and haloacetic acids (HAA5) results here are Colorado’s own from 2020 on, with EPA’s national file for 2012 to 2019. San Luis WSD’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; Colorado’s results run from Aug. 10, 2020 to Aug. 24, 2026.

Testing your own tap

San Luis WSD’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 Colorado certifies.

The lab Colorado certifies closest to the area San Luis WSD serves, in a straight line. Call first: certification is test by test, and not every lab takes samples from homeowners.

  • Sangre De Cristo Laboratory

    Alamosa, CO · about 35 miles

    Certified for bacteria, nitrate, lead and copper, metals, minerals and other inorganics

All 54 certified labs for Colorado

Sources

PWSID CO0112900. Rebuilt from EPA data on Oct. 18, 2026.

Towns it serves

Also in Costilla County

All Colorado utilities

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