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Diagonal Water Department

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
338 people
Connections
133
Water source
Surface water bought from another system
Based in
Diagonal, IA
County
Ringgold
Owner
Local government
The ZIP code it serves

50845

The short answer

1 result is above the limit’s level with no violation recorded, and 1 more is above the health goal. The worst: Haloacetic acids (HAA5), above the limit’s level, no violation. No health-based violations on file since 2016.

What handles it

What was found

Lead and copper: EPA SDWIS monitoring periods ending 2000 to 2022.

Haloacetic acids (HAA5) and total trihalomethanes (TTHM): Iowa’s own results, samples taken from July 8, 2020 to Aug. 4, 2026, with EPA’s 2012 to 2019 file for earlier years.

Above the limit’s level, no violation recorded1

Haloacetic acids (HAA5)

Forms or is added in treatment

Above the limit’s level, no violation

66.2ppb

Highest yearly average, 2020 to 2026

2026 average: 62.3 ppb

Averaged by year, the highest was 66.2 ppb, in 2025, above EPA’s legal limit of 60 ppb. In 2026, the latest year on file, its three samples averaged 62.3 ppb, above the limit. EPA judges this limit on running averages at each sampling point, and recorded no violation for haloacetic acids (HAA5) at this utility since 2020. Results like these with no violation often include water sampled before treatment or blending; the utility’s annual report says what reaches the tap. Earlier, from 2012 to 2019, EPA’s file shows a highest yearly average of 40 ppb, in 2017.

What handles it

No certification claim covers this compound yet.

Above the health goal1

Lead

Comes from pipes, often your own

Above the health goal

1.6ppb

90th percentile, 2020 to 2022

In the latest period, 9 in 10 homes sampled were at or below 1.6 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 limits1

Total trihalomethanes (TTHM)

Forms or is added in treatment

Below EPA’s limits

74.9ppb

Highest yearly average, 2020 to 2026

2026 average: 61.6 ppb

Averaged by year, the highest was 74.9 ppb, in 2020, below EPA’s legal limit of 80 ppb. In 2026, the latest year on file, its three samples averaged 61.6 ppb. Earlier, from 2012 to 2019, EPA’s file shows a highest yearly average of 66 ppb, in 2017.

What handles it

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

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.”

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

Violations since 2016

No health-based violations on file with EPA since 2016. There are 14 monitoring or reporting violations: a sample missed, late or not reported.

What this report can’t tell you

  • Everything else. Haloacetic acids (HAA5) and total trihalomethanes (TTHM) results here are Iowa’s own from 2020 on, with EPA’s national file for 2012 to 2019. Diagonal Water Department’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 July 8, 2020 to Aug. 4, 2026.

Testing your own tap

Diagonal Water Department’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.

The lab Iowa certifies closest to the area Diagonal Water Department serves, in a straight line. Call first: certification is test by test, and not every lab takes samples from homeowners.

  • State Hygienic Laboratory - Ankeny

    Ankeny, IA · about 73 miles

    Certified for bacteria, nitrate, lead and copper, metals, minerals and other inorganics

    (515) 725-1600

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 IA8018040. Rebuilt from EPA data on Oct. 18, 2026.

Also in Ringgold County

All Iowa utilities

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