Koshkonong PWS
What EPA’s and CDC’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
- 212 people
- Connections
- 104
- Water source
- Groundwater
- Based in
- Koshkonong, MO
- County
- Oregon
- Owner
- Local government
The ZIP code it serves
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 itWhat was found
Uranium, nitrate, total trihalomethanes (TTHM), haloacetic acids (HAA5) and arsenic: Missouri’s yearly averages per water system, as CDC’s Environmental Public Health Tracking Network publishes them, 2020 to 2023, with EPA’s 2012 to 2019 file for earlier years.
Chromium (total) and fluoride: EPA’s compliance monitoring file, samples taken from Aug. 14, 2012 to March 11, 2019. Newer results are in the utility’s annual water quality report.
Above the health goal1
Uranium
Comes from the source
1.1ppb
Highest yearly average, 2020
Averaged by year, the highest was 1.1 ppb, in 2020: below EPA’s legal limit of 30 ppb, but above its health goal of zero. That is the only year on file. Earlier, from 2012 to 2019, EPA’s file shows a highest yearly average of 1.1 ppb, in 2019.
What handles it
- NSF/ANSI 58 look for “Uranium”
Below EPA’s limits4
Nitrate
Comes from the source
0.96ppm
Highest yearly average, 2020 to 2023
2023 average: 0.57 ppm
Averaged by year, the highest was 0.96 ppm, in 2022, below EPA’s legal limit of 10 ppm. In 2023, the latest year on file, it averaged 0.57 ppm. Earlier, from 2012 to 2019, EPA’s file shows a highest sample of 2.1 ppm, in 2019.
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
6.5ppb
Highest yearly average, 2020 to 2023
2023 average: 2.5 ppb
Averaged by year, the highest was 6.5 ppb, in 2020, below EPA’s legal limit of 80 ppb. In 2023, the latest year on file, it averaged 2.5 ppb. Earlier, from 2012 to 2019, EPA’s file shows a highest yearly average of 22 ppb, in 2017.
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
1.4ppb
Highest yearly average, 2020 to 2023
2023: not found
Averaged by year, the highest was 1.4 ppb, in 2020, below EPA’s legal limit of 60 ppb. In 2023, the latest year on file, it wasn’t found.
What handles it
No certification claim covers this compound yet.
Chromium (total)
Comes from the source
1.0ppb
Highest yearly average, 2012 to 2019
2019: not found
Averaged by year, the highest was 1.0 ppb, in 2015, below EPA’s legal limit of 100 ppb. In 2019, the latest year on file, it wasn’t found in its one sample.
What handles it
- NSF/ANSI 58 look for “Chromium (Hexavalent) Reduction”
- NSF/ANSI 53 look for “Chromium Reduction”
3 compounds tested and not foundBelow the reporting level in every sample. Not found is not the same as zero.
- Arsenic
- Fluoride
- 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.”
- NSF/ANSI 58
Claim: Uranium
For: Uranium
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 costsViolations since 2016
No health-based violations on file with EPA since 2016. There are 2 monitoring or reporting violations: a sample missed, late or not reported.
What this report can’t tell you
Everything else. Uranium, nitrate, total trihalomethanes (TTHM), haloacetic acids (HAA5) and arsenic results here are Missouri’s yearly averages as CDC publishes them, from 2020 on, with EPA’s national file for 2012 to 2019. Chromium (total) and fluoride come from EPA’s file alone, which ends in 2019. Koshkonong PWS’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; CDC’s yearly averages for Missouri cover 2020 to 2023; EPA’s compliance samples are from Aug. 14, 2012 to March 11, 2019.
Testing your own tap
The lab Missouri certifies closest to the area Koshkonong PWS serves, in a straight line. Call first: certification is test by test, and not every lab takes samples from homeowners.
Perfect Water Testing
Salem, MO · about 67 miles
Certified for bacteria
Missouri State Public Health Laboratory: Coliform and E. coli testing for private wells and other private drinking water sources, in kits from your local public health agency. A free state courier can carry the sample to the lab overnight. The handling fee is $10, by check or money order. Private Drinking Water Bacteriological Testing, Missouri Department of Health and Senior Services.
All 64 certified labs for MissouriSources
- EPA UCMR 5 occurrence data, file of Oct. 15, 2026
- EPA SDWA bulk download (SDWIS federal data), 2026 Q3
- CDC Environmental Public Health Tracking Network, yearly averages Missouri supplied to CDC, 2020 to 2023, read Oct. 8, 2026. TapBuff’s comparisons with EPA’s limits are its own, not CDC’s or Missouri’s.
- EPA Six-Year Review 4 compliance monitoring data, 2012 to 2019, file of Feb. 5, 2024
- Certified labs: Missouri DNR, certified microbiological and chemical laboratories, read Oct. 10, 2026; distances from the Census 2020 ZIP code tabulation area gazetteer
- Limits and goals: each contaminant’s page, with its EPA source.
- How this page is built: methodology.
PWSID MO4010434. Rebuilt from EPA data on Oct. 18, 2026.
What to do next
- Read up on UraniumWhat each one does to health, where it comes from, and the certification claim that addresses it.About Uranium
- Get the utility’s own reportKoshkonong PWS must send you a water quality report every year. It covers contaminants this page does not show, and has newer results than EPA’s national file for the ones here that come from it.How to read it
- Test your own tap for leadYour service line, solder and fixtures decide the lead at your faucet, not the utility’s average.Lead in your water: what to do
- Compare certified filtersWhat the filters certified for these results cost over five years, cartridges included.Compare five-year costs