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Oyens Water Supply

What EPA’s and Iowa’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
92 people
Connections
64
Water source
Groundwater
Based in
Oyens, IA
County
Plymouth
Owner
Local government
Hardness
Very hard
The ZIP code it serves

51045

The short answer

2 results are above the health goal. The worst: Arsenic, 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 2002 to 2023.

Arsenic, fluoride, nitrate and chromium (total): Iowa’s own results, samples taken from Sept. 25, 2020 to July 28, 2026.

Above the health goal2

Arsenic

Comes from the source

Above the health goal

2.7ppb

Highest yearly average, 2021

Averaged by year, the highest was 2.7 ppb, in 2021: below EPA’s legal limit of 10 ppb, but above its health goal of zero. That is the only 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”

Lead

Comes from pipes, often your own

Above the health goal

1.3ppb

90th percentile, 2021 to 2023

In the latest period, 9 in 10 homes sampled were at or below 1.3 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 limits2

Fluoride

Forms or is added in treatment

Below EPA’s limits

0.1ppm

Highest yearly average, 2021

Averaged by year, the highest was 0.1 ppm, in 2021, below EPA’s legal limit of 4.0 ppm. That is the only year on file.

What handles it

Nitrate

Comes from the source

Below EPA’s limits

0.14ppm

Highest sample; found in 2 of 7

2026, one sample: 0.14 ppm

The highest sample, in 2025, was 0.14 ppm, below EPA’s legal limit of 10 ppm. In 2026, the latest year on file, its one sample was 0.14 ppm.

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

    For: 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

Hardness

Very hard, 336 mg/L (19.6 grains per gallon), at its one sampling point, in 2024.

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 19.6 grains per gallon, salt includedSoftener or salt-free conditioner?Iowa water hardness, utility by utility

Violations since 2016

No health-based violations on file with EPA since 2016. There is 1 monitoring or reporting violation: a sample missed, late or not reported.

What this report can’t tell you

  • Everything else. Arsenic, fluoride, nitrate and chromium (total) results here are Iowa’s own from 2020 on, with EPA’s national file for 2012 to 2019. Oyens Water Supply’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; Iowa’s results run from Sept. 25, 2020 to July 28, 2026.

Testing your own tap

Oyens Water Supply’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 Iowa certifies.

No lab Iowa certifies is within 75 miles of the area Oyens Water Supply serves on the state’s list. Some take samples by mail; the state’s page lists them all.

State Hygienic Laboratory at the University of Iowa: Through the Grants-to-Counties program, private well owners in participating counties can have their water tested for total coliform bacteria and nitrate. Start with the county sanitarian at your county health department. No cost in a participating county. The Grants-to-Counties Program, State Hygienic Lab at the University of Iowa.

All 36 certified labs for Iowa

Sources

PWSID IA7561021. Rebuilt from EPA data on Oct. 18, 2026.

Also in Plymouth County

All Iowa utilities

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