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Green Lake 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
1,002 people
Connections
371
Water source
Groundwater
Based in
Green Lake, WI
County
Green Lake
Owner
Local government
Hardness
Very hard
The ZIP code it serves

54941

The short answer

2 results are above the health goal. The worst: Lead, above the health goal. 1 health-based violation since 2016.

What handles it

What was found

Lead and copper: EPA SDWIS monitoring periods ending 2012 to 2023.

Arsenic, nitrate, total trihalomethanes (TTHM), haloacetic acids (HAA5), chromium (total) and fluoride: Wisconsin’s own results, samples taken from April 6, 2020 to Sept. 3, 2026, with EPA’s 2012 to 2019 file for earlier years.

Above the health goal2

Lead

Comes from pipes, often your own

Above the health goal

1.1ppb

90th percentile, 2023

In the latest period, 9 in 10 homes sampled were at or below 1.1 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

Arsenic

Comes from the source

Above the health goal

0.63ppb

Highest yearly average, 2020 to 2026

Averaged by year, the highest was 0.63 ppb, in 2026: below EPA’s legal limit of 10 ppb, but above its health goal of zero. Its highest single sample was 0.85 ppb. 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”

Below EPA’s limits5

Nitrate

Comes from the source

Below EPA’s limits

9.1ppm

Highest sample; found in 26 of 26

2026 average: 7.4 ppm

The highest sample, in 2020, was 9.1 ppm, below EPA’s legal limit of 10 ppm. In 2026, the latest year on file, its three samples averaged 7.4 ppm. Earlier, from 2012 to 2019, EPA’s file shows a highest sample of 9.1 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

Below EPA’s limits

13.1ppb

Highest yearly average, 2020 to 2026

2026, one sample: 4.2 ppb

Averaged by year, the highest was 13.1 ppb, in 2023, below EPA’s legal limit of 80 ppb. In 2026, the latest year on file, its one sample was 4.2 ppb. Earlier, from 2012 to 2019, EPA’s file shows a highest yearly average of 16.3 ppb, in 2016.

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

Below EPA’s limits

1.4ppb

Highest yearly average, 2020 to 2026

2026, one sample: 1.2 ppb

Averaged by year, the highest was 1.4 ppb, in 2022, below EPA’s legal limit of 60 ppb. In 2026, the latest year on file, its one sample was 1.2 ppb. Earlier, from 2012 to 2019, EPA’s file shows a highest yearly average of 1.8 ppb, in 2015.

What handles it

No certification claim covers this compound yet.

Chromium (total)

Comes from the source

Below EPA’s limits

2.0ppb

Highest yearly average, 2020 to 2026

2026 average: 1.9 ppb

Averaged by year, the highest was 2.0 ppb, in 2023, below EPA’s legal limit of 100 ppb. Its highest single sample was 2.7 ppb. In 2026, the latest year on file, its two samples averaged 1.9 ppb. Earlier, from 2012 to 2019, EPA’s file shows a highest yearly average of 0.65 ppb, in 2017.

What handles it

Fluoride

Forms or is added in treatment

Below EPA’s limits

0.079ppm

Highest yearly average, 2020 to 2026

2026 average: 0.065 ppm

Averaged by year, the highest was 0.079 ppm, in 2020, below EPA’s legal limit of 4.0 ppm. Its highest single sample was 0.13 ppm. In 2026, the latest year on file, its two samples averaged 0.065 ppm.

What handles it

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

    For: Lead, Arsenic

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

  • NSF/ANSI 58

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

    For: Lead, Arsenic

    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 water filters for lead, ranked

The best reverse osmosis systems, ranked

Hardness

Very hard, typically 382 mg/L (22.4 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.

Softeners compared at 22.4 grains per gallon, salt includedSoftener or salt-free conditioner?Wisconsin water hardness, utility by utility

Violations since 2016

Contaminant or ruleTypePeriodMeasuredStatus
Lead and Copper Rule RevisionsThe required inventory of lead service lines was not completed or submitted on time.EPA: LSL InventoryOct. 17, 2024—Resolved
Health-based violations only. Resolved and archived mean the utility returned to compliance or the state closed the record. 5 monitoring or reporting violations not shown.

What this report can’t tell you

  • Everything else. Arsenic, nitrate, total trihalomethanes (TTHM), haloacetic acids (HAA5), chromium (total) and fluoride results here are Wisconsin’s own from 2020 on, with EPA’s national file for 2012 to 2019. Green Lake Waterworks’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; Wisconsin’s results run from April 6, 2020 to Sept. 3, 2026.

Testing your own tap

Green Lake Waterworks’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 Wisconsin certifies.

The 3 labs Wisconsin certifies closest to the area Green Lake Waterworks serves, in a straight line. Call first: certification is test by test, and not every lab takes samples from homeowners.

  • Marquette Co. Health Dept. dba Rural Env. Health Alliance

    Montello, WI · about 18 miles

    Certified for bacteria, nitrate

    (608) 297-3135

  • SWD Labs, LLC

    Randolph, WI · about 21 miles

    Certified for bacteria, nitrate

    (920) 326-5193

  • UW-Oshkosh Env. Research & Innovation Ctr

    Oshkosh, WI · about 27 miles

    Certified for bacteria, nitrate, metals

    (920) 424-3148

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 Wisconsin

Sources

PWSID WI4240217. Rebuilt from EPA data on Oct. 18, 2026.

Towns it serves

Also in Green Lake County

All Wisconsin utilities

What to do next