Clark Addition Water System
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
- 189 people
- Connections
- 71
- Water source
- Groundwater
- Based in
- Pasco, WA
- County
- Franklin
- Owner
- Private
- Hardness
- Soft
The ZIP code it serves
The short answer
Nothing in EPA’s and Washington’s records for this utility is above a health goal. That covers nitrate, arsenic and other regulated chemicals, plus lead and copper, not everything. No health-based violations on file since 2016.
What was found
Fluoride, nitrate, arsenic and chromium (total): Washington’s own results, samples taken from June 22, 2020 to June 15, 2026, with EPA’s 2012 to 2019 file for earlier years.
Below EPA’s limits2
Fluoride
Forms or is added in treatment
1.5ppm
Highest yearly average, 2025
Averaged by year, the highest was 1.5 ppm, in 2025, below EPA’s legal limit of 4.0 ppm. That is the only year on file. Earlier, from 2012 to 2019, EPA’s file shows a highest yearly average of 1.8 ppm, in 2016.
What handles it
- NSF/ANSI 58 look for “Fluoride Reduction”
- NSF/ANSI 53 look for “Fluoride”
Nitrate
Comes from the source
1.0ppm
Highest sample; found in 2 of 8
2026: not found
The highest sample, in 2025, was 1.0 ppm, below EPA’s legal limit of 10 ppm. 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 sample of 2.5 ppm, in 2012.
What handles it
- NSF/ANSI 58 look for “Nitrate/Nitrite Reduction”
- NSF/ANSI 53 look for “Nitrate/Nitrite (30 ppm challenge)”
3 compounds tested and not foundBelow the reporting level in every sample. Not found is not the same as zero.
- Arsenic
- Chromium (total)
- Lead
Hardness
Soft, 34 mg/L (2 grains per gallon), at its one sampling point, in 2025.
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.
Violations since 2016
No health-based violations on file with EPA since 2016. There are 5 monitoring or reporting violations: a sample missed, late or not reported.
What this report can’t tell you
Everything else. Fluoride, nitrate, arsenic and chromium (total) results here are Washington’s own from 2020 on, with EPA’s national file for 2012 to 2019. Clark Addition Water System’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 June 22, 2020 to June 15, 2026.
Testing your own tap
The 3 labs Washington certifies closest to the area Clark Addition Water System serves, in a straight line. Call first: certification is test by test, and not every lab takes samples from homeowners.
Matrix Sciences International Inc. dba KTL
Pasco, WA · under a mile
Certified for nitrate, lead and copper, metals, minerals and other inorganics
RJ Lee Group, Inc. Columbia Basin Analytical Laboratories
Pasco, WA · under a mile
Certified for nitrate, lead and copper, metals, minerals and other inorganics
Benton-Franklin Health District Lab
Kennewick, WA · about 16 miles
Certified for bacteria, nitrate, minerals and other inorganics
Sources
- EPA UCMR 5 occurrence data, file of Oct. 15, 2026
- EPA SDWA bulk download (SDWIS federal data), 2026 Q3
- Washington State Department of Health, Office of Drinking Water, results from Jan. 1, 2020 to Sept. 29, 2026, read Oct. 8, 2026
- EPA Six-Year Review 4 compliance monitoring data, 2012 to 2019, file of Feb. 5, 2024
- Certified labs: Washington State Department of Ecology, Lab Accreditation Program, environmental laboratories accredited for drinking water analyses, read Oct. 10, 2026; distances from the Census 2020 ZIP code tabulation area gazetteer
- Hardness: Washington State Department of Health, Office of Drinking Water, results from May 5, 2025 to May 5, 2025, read Oct. 10, 2026
- Limits and goals: each contaminant’s page, with its EPA source.
- How this page is built: methodology.
PWSID WA53AB809. Rebuilt from EPA data on Oct. 18, 2026.
What to do next
- Nothing here is above a health goalIn EPA’s and Washington’s records for this utility. They don’t cover everything, which is why the next step matters.Every contaminant TapBuff tracks
- Get the utility’s own reportClark Addition Water System must send you a water quality report every year. It covers contaminants this page does not show.How to read it
- Test your own tap for leadYour service line, solder and fixtures decide the lead at your faucet, not the utility’s average.Lead in your water: what to do
- Decide if you want a filter at allA filter for taste or chlorine is a preference, not a need. The standards say what each kind can do.NSF/ANSI standards, decoded