Maple Hill Park
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
- 35 people
- Connections
- 22
- Water source
- Groundwater
- Based in
- Coupeville, WA
- County
- Island
- Owner
- Private
- Hardness
- Very hard
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: Nitrate, above the legal limit. 6 health-based violations since 2016.
What handles itWhat was found
Lead and copper: EPA SDWIS monitoring periods ending 2005 to 2025.
Nitrate: Washington’s own results, samples taken from Jan. 21, 2020 to Sept. 10, 2026, with EPA’s 2012 to 2019 file for earlier years.
Arsenic, fluoride and chromium (total): EPA’s compliance monitoring file, samples taken from Oct. 24, 2016 to Sept. 24, 2019. Newer results are in the utility’s annual water quality report.
Above the legal limit1
Nitrate
Comes from the source
16ppm
Highest sample; found in 83 of 83
2026 average: 5.2 ppm
From 2025 to 2026, three samples were above EPA’s legal limit of 10 ppm, the highest 16 ppm in 2025. The next sample at the same point, within 30 days, kept the average above the limit for one; one came back under and one has no follow-up sample on file within 30 days. In 2026, the latest year on file, its 10 samples averaged 5.2 ppm. EPA recorded violations for nitrate at this utility in 2025 and 2026. Earlier, from 2012 to 2019, EPA’s file shows a highest sample of 11.6 ppm, in 2018, and EPA recorded violations in 2012, 2013 and 2018.
What handles it
- NSF/ANSI 58 look for “Nitrate/Nitrite Reduction”
- NSF/ANSI 53 look for “Nitrate/Nitrite (30 ppm challenge)”
Above the health goal2
Arsenic
Comes from the source
1.5ppb
Highest yearly average, 2016 to 2019
2019, one sample: 1.2 ppb
Averaged by year, the highest was 1.5 ppb, in 2016: 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 1.2 ppb.
What handles it
- NSF/ANSI 58 look for “Arsenic (Pentavalent)<=50 ppb Reduction”
- NSF/ANSI 53 look for “Arsenic (Pentavalent)<=50 ppb Reduction”
Lead
Comes from pipes, often your own
1.6ppb
90th percentile, 2023 to 2025
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
- NSF/ANSI 53 look for “Lead Reduction”
- NSF/ANSI 58 look for “Lead Reduction”
Below EPA’s limits1
Fluoride
Forms or is added in treatment
0.55ppm
Highest yearly average, 2016 to 2019
2019: not found
Averaged by year, the highest was 0.55 ppm, in 2016, below EPA’s legal limit of 4.0 ppm. In 2019, the latest year on file, it wasn’t found in its one sample.
What handles it
- NSF/ANSI 58 look for “Fluoride Reduction”
- NSF/ANSI 53 look for “Fluoride”
One compound tested and not foundBelow the reporting level in every sample. Not found is not the same as zero.
- Chromium (total)
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: Nitrate/Nitrite (30 ppm challenge), Arsenic (Pentavalent)<=50 ppb Reduction, Lead Reduction
For: Nitrate, Arsenic, Lead
Other certifiers’ wording: Arsenic (III) (50 ppb influent level)
- NSF/ANSI 58
Claims: Nitrate/Nitrite Reduction, Arsenic (Pentavalent)<=50 ppb Reduction, Lead Reduction
For: Nitrate, Arsenic, Lead
Other certifiers’ wording: Nitrate; 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
Countertop reverse osmosis
- IAPMO listing:NSF/ANSI 42NSF/ANSI 53NSF/ANSI 58NSF/ANSI 401checked Oct. 4, 2026
Certified for: Nitrate, Arsenic, Lead
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: Nitrate, Arsenic, Lead
Culligan 10-Cup Pitcher with ZeroWater Technology (ZEROP10)
Pitcher
- IAPMO listing:NSF/ANSI 42NSF/ANSI 53NSF/ANSI 401checked Oct. 9, 2026
Certified for: Nitrate, Lead
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: Arsenic, Lead
Hardness
Very hard, 240 mg/L (14 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
| Contaminant or rule | Type | Period | Measured | Status |
|---|---|---|---|---|
| Nitrate | A sample was above the legal limit, for a contaminant judged one sample at a time.EPA: Maximum Contaminant Level Violation, Single Sample | Jan. 1, 2026 to March 31, 2026 | 12 MG/L | Archived |
| Nitrate | A sample was above the legal limit, for a contaminant judged one sample at a time.EPA: Maximum Contaminant Level Violation, Single Sample | Jan. 1, 2026 to March 31, 2026 | 11 MG/L | Archived |
| Nitrate | A sample was above the legal limit, for a contaminant judged one sample at a time.EPA: Maximum Contaminant Level Violation, Single Sample | Jan. 1, 2025 to Dec. 31, 2025 | 16 MG/L | Archived |
| Nitrate | A sample was above the legal limit, for a contaminant judged one sample at a time.EPA: Maximum Contaminant Level Violation, Single Sample | Jan. 1, 2025 to Dec. 31, 2025 | 17 MG/L | Archived |
| Nitrate | A sample was above the legal limit, for a contaminant judged one sample at a time.EPA: Maximum Contaminant Level Violation, Single Sample | Jan. 1, 2018 to Dec. 31, 2018 | 11.6 MG/L | Resolved |
| Nitrate | A sample was above the legal limit, for a contaminant judged one sample at a time.EPA: Maximum Contaminant Level Violation, Single Sample | Jan. 1, 2018 to Dec. 31, 2018 | 11.4 MG/L | Resolved |
| Health-based violations only. Resolved and archived mean the utility returned to compliance or the state closed the record. 49 monitoring or reporting violations not shown. | ||||
What this report can’t tell you
Everything else. Nitrate results here are Washington’s own from 2020 on, with EPA’s national file for 2012 to 2019. Arsenic, fluoride and chromium (total) come from EPA’s file alone, which ends in 2019. Maple Hill Park’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 Jan. 21, 2020 to Sept. 10, 2026; EPA’s compliance samples are from Oct. 24, 2016 to Sept. 24, 2019.
Testing your own tap
The 3 labs Washington certifies closest to the area Maple Hill Park serves, in a straight line. Call first: certification is test by test, and not every lab takes samples from homeowners.
Eurofins DW and WW West, Washington Laboratory
Burlington, WA · about 18 miles
Certified for bacteria, nitrate, minerals and other inorganics, disinfection byproducts
Precision Analytical Laboratories, LLC
Everett, WA · about 29 miles
Certified for lead and copper, metals, minerals and other inorganics
Everett Environmental Laboratory
Everett, WA · about 31 miles
Certified for bacteria, nitrate, lead and copper, metals, 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 Sept. 4, 2025 to Sept. 4, 2025, read Oct. 10, 2026
- Limits and goals: each contaminant’s page, with its EPA source.
- How this page is built: methodology.
PWSID WA5309356. 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 Nitrate
- Get the utility’s own reportMaple Hill Park 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