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Lyon - Sioux RWS - Boyden

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
605 people
Connections
244
Water source
Groundwater
Based in
Rock Rapids, IA
County
Lyon
Owner
Private

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 2005 to 2026.

Uranium, arsenic, total trihalomethanes (TTHM), nitrate, haloacetic acids (HAA5), fluoride and chromium (total): Iowa’s own results, samples taken from Feb. 4, 2020 to Aug. 11, 2026, with EPA’s 2012 to 2019 file for earlier years.

Above the health goal3

Uranium

Comes from the source

Above the health goal

19ppb

Highest yearly average, 2022 to 2025

2025, one sample: 16 ppb

Averaged by year, the highest was 19 ppb, in 2022: below EPA’s legal limit of 30 ppb, but above its health goal of zero. In 2025, the latest year on file, its one sample was 16 ppb. Earlier, from 2012 to 2019, EPA’s file shows a highest yearly average of 26 ppb, in 2015.

What handles it

Lead

Comes from pipes, often your own

Above the health goal

5.3ppb

90th percentile, 2024 to 2026

In the latest period, 9 in 10 homes sampled were at or below 5.3 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

Arsenic

Comes from the source

Above the health goal

0.5ppb

Highest yearly average, 2021

Averaged by year, the highest was 0.5 ppb, in 2021: below EPA’s legal limit of 10 ppb, but above its health goal of zero. Its highest single sample was 1.0 ppb. That is the only year on file. Earlier, from 2012 to 2019, EPA’s file shows a highest yearly average of 0.5 ppb, in 2012.

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 limits4

Total trihalomethanes (TTHM)

Forms or is added in treatment

Below EPA’s limits

53.2ppb

Highest yearly average, 2020 to 2026

2026 average: 29 ppb

Averaged by year, the highest was 53.2 ppb, in 2025, below EPA’s legal limit of 80 ppb. Its highest single sample was 80.9 ppb. In 2026, the latest year on file, its six samples averaged 29 ppb. EPA recorded no violation for total trihalomethanes (TTHM) at this utility since 2020. Earlier, from 2012 to 2019, EPA’s file shows a highest yearly average of 39.3 ppb, in 2017.

What handles it

  • NSF/ANSI 53 look for “Trihalomethanes (TTHM) Reduction”
  • NSF/ANSI 58 look for “Trihalomethanes (TTHM) Reduction”

Nitrate

Comes from the source

Below EPA’s limits

6.4ppm

Highest sample; found in 52 of 52

2026 average: 3.9 ppm

The highest sample, in 2022, was 6.4 ppm, below EPA’s legal limit of 10 ppm. In 2026, the latest year on file, its four samples averaged 3.9 ppm. Earlier, from 2012 to 2019, EPA’s file shows a highest sample of 8.7 ppm, in 2016.

What handles it

  • NSF/ANSI 58 look for “Nitrate/Nitrite Reduction”
  • NSF/ANSI 53 look for “Nitrate/Nitrite (30 ppm challenge)”

Haloacetic acids (HAA5)

Forms or is added in treatment

Below EPA’s limits

27.2ppb

Highest yearly average, 2020 to 2026

2026 average: 11.4 ppb

Averaged by year, the highest was 27.2 ppb, in 2025, below EPA’s legal limit of 60 ppb. Its highest single sample was 31 ppb. In 2026, the latest year on file, its six samples averaged 11.4 ppb. Earlier, from 2012 to 2019, EPA’s file shows a highest yearly average of 31.3 ppb, in 2017.

What handles it

No certification claim covers this compound yet.

Fluoride

Forms or is added in treatment

Below EPA’s limits

0.35ppm

Highest yearly average, 2021

Averaged by year, the highest was 0.35 ppm, in 2021, below EPA’s legal limit of 4.0 ppm. Its highest single sample was 0.4 ppm. That is the only year on file. Earlier, from 2012 to 2019, EPA’s file shows a highest yearly average of 0.41 ppm, in 2012.

What handles it

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

    For: Lead, Arsenic

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

  • NSF/ANSI 58

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

    For: Uranium, 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

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. Uranium, arsenic, total trihalomethanes (TTHM), nitrate, haloacetic acids (HAA5), fluoride and chromium (total) results here are Iowa’s own from 2020 on, with EPA’s national file for 2012 to 2019. Lyon - Sioux RWS - Boyden’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 Feb. 4, 2020 to Aug. 11, 2026.

Testing your own tap

Lyon - Sioux RWS - Boyden’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 Lyon - Sioux RWS - Boyden 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 IA6000744. Rebuilt from EPA data on Oct. 18, 2026.

Towns it serves

Also in Lyon County

All Iowa utilities

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