Cobb Waterworks
What EPA’s and Wisconsin’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
- 458 people
- Connections
- 169
- Water source
- Groundwater
- Based in
- Cobb, WI
- County
- Iowa
- Owner
- Local government
- Hardness
- Very hard
The ZIP code it serves
The short answer
2 results are above the health goal. The worst: Arsenic, above the health goal. 1 health-based violation since 2016.
What handles itWhat was found
Arsenic, haloacetic acids (HAA5), total trihalomethanes (TTHM), fluoride, nitrate and chromium (total): Wisconsin’s own results, samples taken from July 14, 2020 to Jan. 12, 2026, with EPA’s 2012 to 2019 file for earlier years.
Uranium: EPA’s compliance monitoring file, samples taken from Sept. 6, 2017 to Dec. 11, 2019. Newer results are in the utility’s annual water quality report.
Above the health goal2
Arsenic
Comes from the source
1.0ppb
Highest yearly average, 2020 to 2026
Averaged by year, the highest was 1.0 ppb, in 2026: below EPA’s legal limit of 10 ppb, but above its health goal of zero. That was also the latest 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
0.56ppb
Highest yearly average, 2017 to 2019
Averaged by year, the highest was 0.56 ppb, in 2019: below EPA’s legal limit of 30 ppb, but above its health goal of zero. Its highest single sample was 0.77 ppb. That was also the latest year on file.
What handles it
- NSF/ANSI 58 look for “Uranium”
Below EPA’s limits4
Haloacetic acids (HAA5)
Forms or is added in treatment
12.5ppb
Highest yearly average, 2022 to 2025
Averaged by year, the highest was 12.5 ppb, in 2025, below EPA’s legal limit of 60 ppb. That was also the latest year on file. Earlier, from 2012 to 2019, EPA’s file shows a highest yearly average of 3.2 ppb, in 2016.
What handles it
No certification claim covers this compound yet.
Total trihalomethanes (TTHM)
Forms or is added in treatment
4.6ppb
Highest yearly average, 2022 to 2025
Averaged by year, the highest was 4.6 ppb, in 2025, below EPA’s legal limit of 80 ppb. That was also the latest year on file. Earlier, from 2012 to 2019, EPA’s file shows a highest yearly average of 4.2 ppb, in 2016.
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
0.14ppm
Highest yearly average, 2020 to 2026
Averaged by year, the highest was 0.14 ppm, in 2026, below EPA’s legal limit of 4.0 ppm. Its highest single sample was 0.16 ppm. That was also the latest year on file. Earlier, from 2012 to 2019, EPA’s file shows a highest yearly average of 0.14 ppm, in 2014.
What handles it
- NSF/ANSI 58 look for “Fluoride Reduction”
- NSF/ANSI 53 look for “Fluoride”
Nitrate
Comes from the source
0.077ppm
Highest sample; found in 6 of 14
2026: not found
The highest sample, in 2021, was 0.077 ppm, below EPA’s legal limit of 10 ppm. In 2026, the latest year on file, it wasn’t found in any of its two samples. Earlier, from 2012 to 2019, EPA’s file shows a highest sample of 0.25 ppm, in 2012.
What handles it
- NSF/ANSI 58 look for “Nitrate/Nitrite Reduction”
- NSF/ANSI 53 look for “Nitrate/Nitrite (30 ppm challenge)”
2 compounds tested and not foundBelow the reporting level in every sample. Not found is not the same as zero.
- Chromium (total)
- 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 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
Countertop reverse osmosis
- IAPMO listing:NSF/ANSI 42NSF/ANSI 53NSF/ANSI 58NSF/ANSI 401checked Oct. 4, 2026
Certified for: Arsenic
Aquasana SmartFlow Reverse Osmosis (AQ-SFRO2)
Under-sink reverse osmosis
- WQA listing:NSF/ANSI 42NSF/ANSI 53NSF/ANSI 58NSF/ANSI 401checked Oct. 9, 2026
Certified for: Arsenic
Brondell Capella RC250 Reverse Osmosis System
Under-sink reverse osmosis
- WQA listing:NSF/ANSI 42NSF/ANSI 53NSF/ANSI 58NSF/ANSI 401checked Oct. 9, 2026
Certified for: Arsenic
Hardness
Very hard, typically 291 mg/L (17 grains per gallon), across 2 sampling points, 2017 to 2026.
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.
Violations since 2016
| Contaminant or rule | Type | Period | Measured | Status |
|---|---|---|---|---|
| Lead and Copper Rule Revisions | The required inventory of lead service lines was not completed or submitted on time.EPA: LSL Inventory | Oct. 17, 2024 | — | Resolved |
| Health-based violations only. Resolved and archived mean the utility returned to compliance or the state closed the record. 32 monitoring or reporting violations not shown. | ||||
What this report can’t tell you
Everything else. Arsenic, haloacetic acids (HAA5), total trihalomethanes (TTHM), fluoride, nitrate and chromium (total) results here are Wisconsin’s own from 2020 on, with EPA’s national file for 2012 to 2019. Uranium comes from EPA’s file alone, which ends in 2019. Cobb Waterworks’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; Wisconsin’s results run from July 14, 2020 to Jan. 12, 2026; EPA’s compliance samples are from Sept. 6, 2017 to Dec. 11, 2019.
Testing your own tap
The 3 labs Wisconsin certifies closest to the area Cobb Waterworks serves, in a straight line. Call first: certification is test by test, and not every lab takes samples from homeowners.
Iowa County
Dodgeville, WI · about 9 miles
Certified for bacteria
LV Labs WW, LLC
Lancaster, WI · about 21 miles
Certified for bacteria, nitrate
Lafayette County Health Department
Darlington, WI · about 23 miles
Certified for bacteria, nitrate
Wisconsin State Laboratory of Hygiene: Well water test kits ordered by phone and shipped free; you pay to mail the sample back, and the lab bills you after testing. Tests run from bacteria alone to a homeowner package covering bacteria, nitrate, fluoride, metals, hardness, volatile organic compounds and atrazine. Bacteria is $35, nitrate $35, lead $38, and the homeowner package $450, as of July 1, 2026. Public Environmental and Water Testing Prices, Wisconsin State Laboratory of Hygiene.
All 156 certified labs for WisconsinSources
- EPA UCMR 5 occurrence data, file of Oct. 15, 2026
- EPA SDWA bulk download (SDWIS federal data), 2026 Q3
- Wisconsin Department of Natural Resources, Drinking Water Program, results from Jan. 2, 2020 to Oct. 5, 2026, read Oct. 8, 2026
- EPA Six-Year Review 4 compliance monitoring data, 2012 to 2019, file of Feb. 5, 2024
- Certified labs: Wisconsin DNR and DATCP, certified and approved drinking water laboratories, read Oct. 10, 2026; distances from the Census 2020 ZIP code tabulation area gazetteer
- Hardness: Wisconsin Department of Natural Resources, Drinking Water Program, results from Sept. 6, 2017 to Jan. 12, 2026, read Oct. 10, 2026
- Limits and goals: each contaminant’s page, with its EPA source.
- How this page is built: methodology.
PWSID WI1250076. Rebuilt from EPA data on Oct. 18, 2026.
What to do next
- Read up on the 2 results above a lineWhat each one does to health, where it comes from, and the certification claim that addresses it.Start with Arsenic
- Get the utility’s own reportCobb Waterworks 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