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Town of Westby

What EPA’s and Montana’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
172 people
Connections
107
Water source
Surface water bought from another system
Based in
Westby, MT
County
Sheridan
Owner
Local government
The ZIP code it serves

59275

The short answer

3 results are 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

Lead and copper: EPA SDWIS monitoring periods ending 2000 to 2025.

Arsenic, haloacetic acids (HAA5), total trihalomethanes (TTHM) and nitrate: Montana’s own results, samples taken from March 10, 2020 to April 7, 2026, with EPA’s 2012 to 2019 file for earlier years.

Uranium, fluoride and chromium (total): EPA’s compliance monitoring file, samples taken from Sept. 23, 2013 to Sept. 19, 2018. Newer results are in the utility’s annual water quality report.

Above the health goal3

Uranium

Comes from the source

Above the health goal

20ppb

Highest yearly average, 2013 to 2018

2018, one sample: 15.2 ppb

Averaged by year, the highest was 20 ppb, in 2013: below EPA’s legal limit of 30 ppb, but above its health goal of zero. In 2018, the latest year on file, its one sample was 15.2 ppb.

What handles it

Arsenic

Comes from the source

Above the health goal

2.7ppb

Highest yearly average, 2020

Averaged by year, the highest was 2.7 ppb, in 2020: below EPA’s legal limit of 10 ppb, but above its health goal of zero. Its highest single sample was 3.0 ppb. That is the only year on file. Earlier, from 2012 to 2019, EPA’s file shows a highest yearly average of 30.7 ppb, in 2012, and EPA recorded violations in 2012, 2014 and 2015.

What handles it

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

Lead

Comes from pipes, often your own

Above the health goal

1.0ppb

90th percentile, 2023 to 2025

In the latest period, 9 in 10 homes sampled were at or below 1.0 ppb, below EPA’s action level of 15 ppb. The action level drops to 10 ppb on Nov. 1, 2027. EPA’s health goal for lead is zero.

What handles it

Below EPA’s limits4

Haloacetic acids (HAA5)

Forms or is added in treatment

Below EPA’s limits

25ppb

Highest yearly average, 2021 to 2026

2026, one sample: 11 ppb

Averaged by year, the highest was 25 ppb, in 2025, below EPA’s legal limit of 60 ppb. In 2026, the latest year on file, its one sample was 11 ppb.

What handles it

No certification claim covers this compound yet.

Total trihalomethanes (TTHM)

Forms or is added in treatment

Below EPA’s limits

26ppb

Highest yearly average, 2021 to 2026

2026, one sample: 15 ppb

Averaged by year, the highest was 26 ppb, in 2025, below EPA’s legal limit of 80 ppb. In 2026, the latest year on file, its one sample was 15 ppb. Earlier, from 2012 to 2019, EPA’s file shows a highest yearly average of 2.5 ppb, in 2018.

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

0.3ppm

Highest yearly average, 2014 to 2018

2018, one sample: 0.2 ppm

Averaged by year, the highest was 0.3 ppm, in 2014, below EPA’s legal limit of 4.0 ppm. In 2018, the latest year on file, its one sample was 0.2 ppm.

What handles it

Nitrate

Comes from the source

Below EPA’s limits

0.57ppm

One sample

2020, one sample: 0.57 ppm

The highest sample, in 2020, was 0.57 ppm, below EPA’s legal limit of 10 ppm. That is the only year on file, and its one sample was 0.57 ppm. Earlier, from 2012 to 2019, EPA’s file shows a highest sample of 2.3 ppm, in 2013.

What handles it

  • NSF/ANSI 58 look for “Nitrate/Nitrite Reduction”
  • NSF/ANSI 53 look for “Nitrate/Nitrite (30 ppm challenge)”
One compound tested and not foundBelow the reporting level in every sample. Not found is not the same as zero.
  • Chromium (total)

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: Arsenic (Pentavalent)<=50 ppb Reduction, Lead Reduction

    For: Arsenic, Lead

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

  • NSF/ANSI 58

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

    For: Uranium, Arsenic, Lead

    Other certifiers’ wording: Arsenic (Pentavalent)<=300 ppb Reduction; Arsenic (V) (300 ppb influent level)

At the tap, or for the whole house?

Lead and copper usually come from pipes and fixtures inside or near your home. A whole-house system sits where water enters, so it cannot catch what your own plumbing adds after it. For those, the filter that counts is the one at the tap. 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

The best water filters for lead, ranked

Violations since 2016

No health-based violations on file with EPA since 2016. There are 4 monitoring or reporting violations: a sample missed, late or not reported.

What this report can’t tell you

  • Everything else. Arsenic, haloacetic acids (HAA5), total trihalomethanes (TTHM) and nitrate results here are Montana’s own from 2020 on, with EPA’s national file for 2012 to 2019. Uranium, fluoride and chromium (total) come from EPA’s file alone, which ends in 2019. Town of Westby’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; Montana’s results run from March 10, 2020 to April 7, 2026; EPA’s compliance samples are from Sept. 23, 2013 to Sept. 19, 2018.

Testing your own tap

Town of Westby’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 Montana certifies.

The lab Montana certifies closest to the area Town of Westby serves, in a straight line. Call first: certification is test by test, and not every lab takes samples from homeowners.

  • Astro-Chem Lab Inc.

    Williston, ND · about 50 miles

    Certified for bacteria

    (701) 572-7355

Montana State Environmental Laboratory: Private well testing packages for bacteria, metals, nutrients, anions, organic chemicals and more, open to the public. Samples can be mailed, sent by the lab's free courier, or dropped off at the lab. Environmental Laboratory, Montana Department of Public Health and Human Services.

All 36 certified labs for Montana

Sources

PWSID MT0000355. Rebuilt from EPA data on Oct. 18, 2026.

Also in Sheridan County

All Montana utilities

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