Skip to content
TapBuff
ZIP

Roza Heights Water Assn

What EPA’s and Washington’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
110 people
Connections
52
Water source
Groundwater
Based in
Prosser, WA
County
Benton
Owner
Private
Hardness
Very hard

The short answer

1 result is 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

Arsenic, nitrate, fluoride, total trihalomethanes (TTHM), haloacetic acids (HAA5) and chromium (total): Washington’s own results, samples taken from March 9, 2020 to Aug. 21, 2026, with EPA’s 2012 to 2019 file for earlier years.

Above the health goal1

Arsenic

Comes from the source

Above the health goal

2.7ppb

Highest yearly average, 2020 to 2023

2023, one sample: 2.5 ppb

Averaged by year, the highest was 2.7 ppb, in 2020: below EPA’s legal limit of 10 ppb, but above its health goal of zero. In 2023, the latest year on file, its one sample was 2.5 ppb.

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

Nitrate

Comes from the source

Below EPA’s limits

6.8ppm

Highest sample; found in 11 of 11

2025, one sample: 4.5 ppm

The highest sample, in 2024, was 6.8 ppm, below EPA’s legal limit of 10 ppm. In 2025, the latest year on file, its one sample was 4.5 ppm. Earlier, from 2012 to 2019, EPA’s file shows a highest sample of 7.0 ppm, in 2012.

What handles it

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

Fluoride

Forms or is added in treatment

Below EPA’s limits

0.32ppm

Highest yearly average, 2020

Averaged by year, the highest was 0.32 ppm, in 2020, below EPA’s legal limit of 4.0 ppm. That is the only year on file.

What handles it

Total trihalomethanes (TTHM)

Forms or is added in treatment

Below EPA’s limits

5.4ppb

Highest yearly average, 2022 to 2026

2026: not found

Averaged by year, the highest was 5.4 ppb, in 2022, below EPA’s legal limit of 80 ppb. 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 yearly average of 14 ppb, in 2012.

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

2.3ppb

Highest yearly average, 2022 to 2026

2026: not found

Averaged by year, the highest was 2.3 ppb, in 2022, below EPA’s legal limit of 60 ppb. In 2026, the latest year on file, it wasn’t found in its one sample. Earlier, from 2012 to 2019, EPA’s file shows a highest yearly average of 4.2 ppb, in 2012.

What handles it

No certification claim covers this compound yet.

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

    Claim: Arsenic (Pentavalent)<=50 ppb Reduction

    For: Arsenic

    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

Compare five-year costs

The best reverse osmosis systems, ranked

Hardness

Very hard, 299 mg/L (17.5 grains per gallon), at its one sampling point, in 2020.

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 17.5 grains per gallon, salt includedSoftener or salt-free conditioner?Washington water hardness, utility by utility

Violations since 2016

No health-based violations on file with EPA since 2016. There are 3 monitoring or reporting violations: a sample missed, late or not reported.

What this report can’t tell you

  • Everything else. Arsenic, nitrate, fluoride, total trihalomethanes (TTHM), haloacetic acids (HAA5) and chromium (total) results here are Washington’s own from 2020 on, with EPA’s national file for 2012 to 2019. Roza Heights Water Assn’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; Washington’s results run from March 9, 2020 to Aug. 21, 2026.

Testing your own tap

Roza Heights Water Assn’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 Washington certifies.

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

All 84 certified labs for Washington

Sources

PWSID WA5374800. Rebuilt from EPA data on Oct. 18, 2026.

Also in Benton County

All Washington utilities

What to do next