Tamoshan
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
- 260 people
- Connections
- 94
- Water source
- Groundwater
- Based in
- Olympia, WA
- County
- Thurston
- Owner
- Local government
- Hardness
- Soft
The ZIP code it serves
The short answer
1 result is above EPA’s legal limit, and 1 more is above the health goal. The worst: Haloacetic acids (HAA5), above the legal limit. 10 health-based violations since 2016.
What handles itWhat was found
Lead and copper: EPA SDWIS monitoring periods ending 2002 to 2025.
Haloacetic acids (HAA5), total trihalomethanes (TTHM), nitrate, arsenic, chromium (total) and fluoride: Washington’s own results, samples taken from Feb. 21, 2020 to April 8, 2026, with EPA’s 2012 to 2019 file for earlier years.
Above the legal limit1
Haloacetic acids (HAA5)
Forms or is added in treatment
103ppb
Highest yearly average, 2020 to 2026
2026 average: 25.5 ppb
Averaged by year, the highest was 103 ppb, in 2021, above EPA’s legal limit of 60 ppb. Its highest single sample was 131 ppb. In 2026, the latest year on file, its two samples averaged 25.5 ppb. EPA recorded violations for haloacetic acids (HAA5) at this utility in 2021, 2022 and 2023. Earlier, from 2012 to 2019, EPA’s file shows a highest yearly average of 54.4 ppb, in 2018.
What handles it
No certification claim covers this compound yet.
Above the health goal1
Lead
Comes from pipes, often your own
6.6ppb
90th percentile, 2023 to 2025
In the latest period, 9 in 10 homes sampled were at or below 6.6 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
- NSF/ANSI 53 look for “Lead Reduction”
- NSF/ANSI 58 look for “Lead Reduction”
Below EPA’s limits2
Total trihalomethanes (TTHM)
Forms or is added in treatment
63.9ppb
Highest yearly average, 2020 to 2026
2026 average: 46.6 ppb
Averaged by year, the highest was 63.9 ppb, in 2025, below EPA’s legal limit of 80 ppb. Its highest single sample was 150 ppb. In 2026, the latest year on file, its two samples averaged 46.6 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 72.7 ppb, in 2016, and EPA recorded a violation 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
0.5ppm
Highest sample; found in 2 of 7
2025: not found
The highest sample, in 2022, was 0.5 ppm, below EPA’s legal limit of 10 ppm. In 2025, the latest year on file, it wasn’t found in its one sample.
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)
- Fluoride
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: Lead Reduction
For: Lead
- NSF/ANSI 58
Claim: Lead Reduction
For: 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
Brita Tahoe Pitcher with Elite Filter (OB60, OB06)
Pitcher
- WQA listing:NSF/ANSI 42NSF/ANSI 53NSF/ANSI 401checked Oct. 13, 2026
- IAPMO listing:NSF/ANSI 53checked Oct. 13, 2026
Certified for: Lead
Brita Everyday Pitcher with Elite Filter (OB46, OB06)
Pitcher
- WQA listing:NSF/ANSI 42NSF/ANSI 53NSF/ANSI 401checked Oct. 13, 2026
Certified for: Lead
PUR PLUS 11-Cup Pitcher (PPT111W)
Pitcher
- NSF listing:NSF/ANSI 42NSF/ANSI 53NSF/ANSI 401checked Oct. 4, 2026
- WQA listing:NSF/ANSI 42NSF/ANSI 53NSF/ANSI 401checked Oct. 4, 2026
- IAPMO listing:NSF/ANSI 42NSF/ANSI 53NSF/ANSI 401checked Oct. 4, 2026
Certified for: Lead
ZeroWater 10 Cup Pitcher (ZP-010)
Pitcher
- IAPMO listing:NSF/ANSI 42NSF/ANSI 53checked Oct. 4, 2026
Certified for: Lead
Culligan 10-Cup Pitcher with ZeroWater Technology (ZEROP10)
Pitcher
- IAPMO listing:NSF/ANSI 42NSF/ANSI 53NSF/ANSI 401checked Oct. 9, 2026
Certified for: Lead
Hardness
Soft, 44 mg/L (2.6 grains per gallon), at its one sampling point, in 2023.
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
| Contaminant or rule | Type | Period | Measured | Status |
|---|---|---|---|---|
| Total Haloacetic Acids (HAA5) | The running average was above the legal limit.EPA: Maximum Contaminant Level Violation, Average | April 1, 2023 to June 30, 2023 | 61 UG/L | Resolved |
| Total Haloacetic Acids (HAA5) | The running average was above the legal limit.EPA: Maximum Contaminant Level Violation, Average | Jan. 1, 2023 to March 31, 2023 | 76.1 UG/L | Resolved |
| Total Haloacetic Acids (HAA5) | The running average was above the legal limit.EPA: Maximum Contaminant Level Violation, Average | Oct. 1, 2022 to Dec. 31, 2022 | 95.4 UG/L | Resolved |
| Total Haloacetic Acids (HAA5) | The running average was above the legal limit.EPA: Maximum Contaminant Level Violation, Average | July 1, 2022 to Sept. 30, 2022 | 103 UG/L | Resolved |
| Total Haloacetic Acids (HAA5) | The running average was above the legal limit.EPA: Maximum Contaminant Level Violation, Average | April 1, 2022 to June 30, 2022 | 107 UG/L | Resolved |
| Total Haloacetic Acids (HAA5) | The running average was above the legal limit.EPA: Maximum Contaminant Level Violation, Average | Jan. 1, 2022 to March 31, 2022 | 114 UG/L | Resolved |
| Total Haloacetic Acids (HAA5) | The running average was above the legal limit.EPA: Maximum Contaminant Level Violation, Average | Oct. 1, 2021 to Dec. 31, 2021 | 103 UG/L | Resolved |
| Total Haloacetic Acids (HAA5) | The running average was above the legal limit.EPA: Maximum Contaminant Level Violation, Average | July 1, 2021 to Sept. 30, 2021 | 101 UG/L | Resolved |
| TTHM | The running average was above the legal limit.EPA: Maximum Contaminant Level Violation, Average | April 1, 2017 to June 30, 2017 | 96.2 UG/L | Resolved |
| TTHM | The running average was above the legal limit.EPA: Maximum Contaminant Level Violation, Average | Jan. 1, 2017 to March 31, 2017 | 99.4 UG/L | Resolved |
| Health-based violations only. Resolved and archived mean the utility returned to compliance or the state closed the record. 6 monitoring or reporting violations not shown. | ||||
What this report can’t tell you
Everything else. Haloacetic acids (HAA5), total trihalomethanes (TTHM), nitrate, arsenic, chromium (total) and fluoride results here are Washington’s own from 2020 on, with EPA’s national file for 2012 to 2019. Tamoshan’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 Feb. 21, 2020 to April 8, 2026.
Testing your own tap
The 3 labs Washington certifies closest to the area Tamoshan serves, in a straight line. Call first: certification is test by test, and not every lab takes samples from homeowners.
Olympic Analytical LLC dba Vanguard Laboratory
Olympia, WA · under a mile
Certified for bacteria, nitrate
Thurston County Health Department Laboratory
Olympia, WA · about 7 miles
Certified for bacteria, nitrate
Grays Harbor County Water Testing Lab
Montesano, WA · about 29 miles
Certified for bacteria, nitrate
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 July 19, 2023 to July 19, 2023, read Oct. 10, 2026
- Limits and goals: each contaminant’s page, with its EPA source.
- How this page is built: methodology.
PWSID WA5387140. Rebuilt from EPA data on Oct. 18, 2026.
What to do next
- Read up on the 2 results above a lineWhat each one does to health, where it comes from, and the certification claim that addresses it.Start with Haloacetic acids (HAA5)
- Get the utility’s own reportTamoshan 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
- Compare certified filtersWhat the filters certified for these results cost over five years, cartridges included.Compare five-year costs