Cape San Juan Water District
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
- 164 people
- Connections
- 145
- Water source
- Groundwater
- Based in
- Friday Harbor, WA
- County
- San Juan
- Owner
- Local government
The ZIP code it serves
The short answer
1 result is above EPA’s legal limit, and 2 more are above the health goal. The worst: Total trihalomethanes (TTHM), above the legal limit. 13 health-based violations since 2016.
What handles itWhat was found
Lead and copper: EPA SDWIS monitoring periods ending 2005 to 2025.
Copper: EPA’s file records a utility’s copper only when it exceeds the action level. The last here was 1.4 ppm, for the period ending June 30, 2002. None since is on file, so it is not counted as a current finding.
Total trihalomethanes (TTHM), haloacetic acids (HAA5), nitrate and fluoride: Washington’s own results, samples taken from March 17, 2020 to Sept. 15, 2026, with EPA’s 2012 to 2019 file for earlier years.
Arsenic and chromium (total): EPA’s compliance monitoring file, samples taken from Sept. 18, 2017 to Feb. 25, 2019. Newer results are in the utility’s annual water quality report.
Above the legal limit1
Total trihalomethanes (TTHM)
Forms or is added in treatment
118ppb
Highest yearly average, 2020 to 2026
2026 average: 80.3 ppb
Averaged by year, the highest was 118 ppb, in 2022, above EPA’s legal limit of 80 ppb. Its highest single sample was 179 ppb. In 2026, the latest year on file, its three samples averaged 80.3 ppb. EPA recorded violations for total trihalomethanes (TTHM) at this utility in 2021, 2022, 2023 and 2024. Earlier, from 2012 to 2019, EPA’s file shows a highest yearly average of 111 ppb, in 2013.
What handles it
- NSF/ANSI 53 look for “Trihalomethanes (TTHM) Reduction”
- NSF/ANSI 58 look for “Trihalomethanes (TTHM) Reduction”
Above the health goal2
Lead
Comes from pipes, often your own
5.1ppb
90th percentile, 2023 to 2025
In the latest period, 9 in 10 homes sampled were at or below 5.1 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”
Arsenic
Comes from the source
2.0ppb
Highest yearly average, 2017 to 2019
2019, one sample: 2.0 ppb
Averaged by year, the highest was 2.0 ppb, in 2017: below EPA’s legal limit of 10 ppb, but above its health goal of zero. In 2019, the latest year on file, its one sample was 2.0 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
Haloacetic acids (HAA5)
Forms or is added in treatment
16ppb
Highest yearly average, 2020 to 2026
2026 average: 16 ppb
Averaged by year, the highest was 16 ppb, in 2024, below EPA’s legal limit of 60 ppb. Its highest single sample was 23.5 ppb. In 2026, the latest year on file, its three samples averaged 16 ppb. Earlier, from 2012 to 2019, EPA’s file shows a highest yearly average of 17.7 ppb, in 2019.
What handles it
No certification claim covers this compound yet.
Nitrate
Comes from the source
2.1ppm
Highest sample; found in 7 of 7
2026, one sample: 1.9 ppm
The highest sample, in 2022, was 2.1 ppm, below EPA’s legal limit of 10 ppm. In 2026, the latest year on file, its one sample was 1.9 ppm. Earlier, from 2012 to 2019, EPA’s file shows a highest sample of 2.4 ppm, in 2016.
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
0.2ppm
Highest yearly average, 2025
Averaged by year, the highest was 0.2 ppm, in 2025, below EPA’s legal limit of 4.0 ppm. That is the only year on file.
What handles it
- NSF/ANSI 58 look for “Fluoride Reduction”
- NSF/ANSI 53 look for “Fluoride”
Chromium (total)
Comes from the source
1.0ppb
Highest yearly average, 2017
Averaged by year, the highest was 1.0 ppb, in 2017, below EPA’s legal limit of 100 ppb. That is the only year on file.
What handles it
- NSF/ANSI 58 look for “Chromium (Hexavalent) Reduction”
- NSF/ANSI 53 look for “Chromium 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.”
- NSF/ANSI 53
Claims: Trihalomethanes (TTHM) Reduction, Lead Reduction, Arsenic (Pentavalent)<=50 ppb Reduction
For: Total trihalomethanes (TTHM), Lead, Arsenic
Other certifiers’ wording: VOC Reduction; Arsenic (III) (50 ppb influent level)
- NSF/ANSI 58
Claims: Trihalomethanes (TTHM) Reduction, Lead Reduction, Arsenic (Pentavalent)<=50 ppb Reduction
For: Total trihalomethanes (TTHM), 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
Aquasana SmartFlow Reverse Osmosis (AQ-SFRO2)
Under-sink reverse osmosis
- WQA listing:NSF/ANSI 42NSF/ANSI 53NSF/ANSI 58NSF/ANSI 401checked Oct. 9, 2026
Certified for: Total trihalomethanes (TTHM), Lead, Arsenic
Brondell Capella RC250 Reverse Osmosis System
Under-sink reverse osmosis
- WQA listing:NSF/ANSI 42NSF/ANSI 53NSF/ANSI 58NSF/ANSI 401checked Oct. 9, 2026
Certified for: Total trihalomethanes (TTHM), Lead, Arsenic
Countertop reverse osmosis
- IAPMO listing:NSF/ANSI 42NSF/ANSI 53NSF/ANSI 58NSF/ANSI 401checked Oct. 4, 2026
Certified for: Total trihalomethanes (TTHM), Lead, Arsenic
Aquasana Clean Water Machine (AQ-CWM2)
Countertop
- WQA listing:NSF/ANSI 42NSF/ANSI 53NSF/ANSI 401checked Oct. 9, 2026
Certified for: Total trihalomethanes (TTHM), Lead
Brita Hub Countertop Water Filter System (87340)
Countertop
- WQA listing:NSF/ANSI 42NSF/ANSI 53NSF/ANSI 401checked Oct. 9, 2026
- IAPMO listing:NSF/ANSI 53checked Oct. 9, 2026
Certified for: Total trihalomethanes (TTHM), Lead
Violations since 2016
| Contaminant or rule | Type | Period | Measured | Status |
|---|---|---|---|---|
| TTHM | The running average was above the legal limit.EPA: Maximum Contaminant Level Violation, Average | April 1, 2024 to June 30, 2024 | 86.6 UG/L | Archived |
| TTHM | The running average was above the legal limit.EPA: Maximum Contaminant Level Violation, Average | Oct. 1, 2023 to Dec. 31, 2023 | 82.4 UG/L | Archived |
| TTHM | The running average was above the legal limit.EPA: Maximum Contaminant Level Violation, Average | July 1, 2023 to Sept. 30, 2023 | 83.1 UG/L | Archived |
| TTHM | The running average was above the legal limit.EPA: Maximum Contaminant Level Violation, Average | April 1, 2023 to June 30, 2023 | 105 UG/L | Archived |
| TTHM | The running average was above the legal limit.EPA: Maximum Contaminant Level Violation, Average | Jan. 1, 2023 to March 31, 2023 | 102 UG/L | Archived |
| TTHM | The running average was above the legal limit.EPA: Maximum Contaminant Level Violation, Average | Oct. 1, 2022 to Dec. 31, 2022 | 118 UG/L | Archived |
| TTHM | The running average was above the legal limit.EPA: Maximum Contaminant Level Violation, Average | July 1, 2022 to Sept. 30, 2022 | 108 UG/L | Archived |
| TTHM | The running average was above the legal limit.EPA: Maximum Contaminant Level Violation, Average | April 1, 2022 to June 30, 2022 | 87.8 UG/L | Archived |
| TTHM | The running average was above the legal limit.EPA: Maximum Contaminant Level Violation, Average | Jan. 1, 2022 to March 31, 2022 | 87.8 UG/L | Archived |
| TTHM | The running average was above the legal limit.EPA: Maximum Contaminant Level Violation, Average | Oct. 1, 2021 to Dec. 31, 2021 | 99.7 UG/L | Archived |
| TTHM | The running average was above the legal limit.EPA: Maximum Contaminant Level Violation, Average | July 1, 2021 to Sept. 30, 2021 | 110 UG/L | Archived |
| TTHM | The running average was above the legal limit.EPA: Maximum Contaminant Level Violation, Average | April 1, 2021 to June 30, 2021 | 113 UG/L | Archived |
| TTHM | The running average was above the legal limit.EPA: Maximum Contaminant Level Violation, Average | Jan. 1, 2021 to March 31, 2021 | 85 UG/L | Archived |
| Health-based violations only. Resolved and archived mean the utility returned to compliance or the state closed the record. 5 monitoring or reporting violations not shown. | ||||
What this report can’t tell you
Everything else. Total trihalomethanes (TTHM), haloacetic acids (HAA5), nitrate and fluoride results here are Washington’s own from 2020 on, with EPA’s national file for 2012 to 2019. Arsenic and chromium (total) come from EPA’s file alone, which ends in 2019. Cape San Juan Water District’s own annual report, which it must send you every year, has newer results for those and 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 17, 2020 to Sept. 15, 2026; EPA’s compliance samples are from Sept. 18, 2017 to Feb. 25, 2019.
Testing your own tap
The 3 labs Washington certifies closest to the area Cape San Juan Water District serves, in a straight line. Call first: certification is test by test, and not every lab takes samples from homeowners.
Exact Scientific Services, Inc.
Ferndale, WA · about 30 miles
Certified for bacteria, nitrate, lead and copper, metals, minerals and other inorganics, organic chemicals, disinfection byproducts
Eurofins DW and WW West, Washington Laboratory
Burlington, WA · about 35 miles
Certified for bacteria, nitrate, minerals and other inorganics, disinfection byproducts
Clallam County Environmental Laboratory
Port Angeles, WA · about 46 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
- Limits and goals: each contaminant’s page, with its EPA source.
- How this page is built: methodology.
PWSID WA5311065. Rebuilt from EPA data on Oct. 18, 2026.
What to do next
- Read up on the 3 results above a lineWhat each one does to health, where it comes from, and the certification claim that addresses it.Start with Total trihalomethanes (TTHM)
- Get the utility’s own reportCape San Juan Water District must send you a water quality report every year. It covers contaminants this page does not show, and has newer results than EPA’s national file for the ones here that come from it.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