Tap Water Quality Report
Tap water quality in Sammamish, Washington
Tap water in Sammamish, Washington receives a grade of F (50/100) from TapWaterSafety.org. It's served by SAMMAMISH PLATEAU WATER & SEWER. The most significant water quality concerns are: PFAS contamination; Perfluorohexane sulfonate (PFHXS) significantly above health guideline; Total PFOS and PFOA significantly above health guideline; Haloacetic acids (HAA9) significantly above health guideline. Data sources: EPA SDWIS, EPA ECHO, EWG Tap Water Database.
What's in Sammamish's tap water
Top water quality concerns identified by the EPA and Environmental Working Group across the utility serving Sammamish.
PFAS contamination
Severe concernPerfluorononanoic acid (PFNA), Perfluorooctane sulfonate (PFOS) detected. PFAS are persistent chemicals linked to cancer and immune effects with no known safe exposure threshold.
Perfluorohexane sulfonate (PFHXS) significantly above health guideline
Moderate concernPerfluorohexane sulfonate (PFHXS) detected at 8.19 ppt, 8189x above the EWG health guideline of 0.001 ppt.
Total PFOS and PFOA significantly above health guideline
Moderate concernTotal PFOS and PFOA detected at 12.4 ppt, 1770x above the EWG health guideline of 0.007 ppt.
Haloacetic acids (HAA9) significantly above health guideline
Moderate concernHaloacetic acids (HAA9) detected at 14.4 ppb, 240x above the EWG health guideline of 0.06 ppb.
Recommended filters for Sammamish
Filters matched to the specific contaminants in Sammamish's water supply.
Reverse Osmosis or NSF P473 certified carbon
$80-$750Activated carbon and RO are the only technologies proven to remove PFAS at certified levels.
Carbon block (NSF/ANSI 42 + 53)
$40-$750Activated carbon is highly effective for disinfection byproducts like TTHM and HAA5.
Disclosure: TapWaterSafety earns a commission from purchases made through these links. This does not influence our scoring methodology or filter selection.
All contaminants detected in Sammamish's tap water
Every contaminant identified, compared side-by-side against US EPA legal limits, the EU Drinking Water Directive (2020/2184), WHO Guidelines, and California's Public Health Goal. Why we show multiple standards →
| Contaminant | Detected | EWG US health-based |
EPA US legal |
EU DWD Europe |
WHO global |
CA PHG strictest US |
Tested sample year |
Status |
|---|---|---|---|---|---|---|---|---|
| Perfluorooctane sulfonate (PFOS) PFAS |
5.79 ppt | 0.3 | 4.0 | 100 | 100 | 1 | — | EPA violation |
| Perfluorohexane sulfonate (PFHXS) PFAS |
8.19 ppt | 0.001 | 10.0 | — | — | — | — | 8189× over |
| Total PFOS and PFOA PFAS |
12.4 ppt | 0.007 | — | 100 | 100 | 0.007 | — | 1770× over |
| Haloacetic acids (HAA9) Disinfection byproduct |
14.4 ppb | 0.06 | — | — | — | — | — | 240× over |
| Haloacetic acids (HAA5) Disinfection byproduct |
13.7 ppb | 0.1 | 60.0 | 60 | — | — | — | 137× over |
| Total trihalomethanes (TTHMs) Disinfection byproduct |
17.8 ppb | 0.15 | 80.0 | 100 | — | — | — | 118× over |
| Perfluorononanoic acid (PFNA) PFAS |
0.582 ppt | 0.006 | 10.0 | — | — | — | — | 97× over |
| Trichloroacetic acid Disinfection byproduct |
7.36 ppb | 0.1 | — | — | — | — | — | 74× over |
| Chloroform Disinfection byproduct |
14.8 ppb | 0.4 | — | — | — | — | — | 37× over |
| Bromodichloromethane Disinfection byproduct |
2.16 ppb | 0.06 | — | — | — | — | — | 36× over |
| Dichloroacetic acid Disinfection byproduct |
5.99 ppb | 0.2 | — | — | — | — | — | 30× over |
| Bromochloroacetic acid Disinfection byproduct |
0.197 ppb | 0.02 | — | — | — | — | — | 9.9× over |
| Dibromochloromethane Disinfection byproduct |
0.578 ppb | 0.1 | — | — | — | — | — | 5.8× over |
| Perfluorooctanoic acid (PFOA) PFAS |
0.514 ppt | 0.09 | 4.0 | 100 | 100 | 0.007 | — | 5.7× over |
| Chromium (hexavalent) Heavy metal |
0.109 ppb | 0.02 | — | — | — | — | — | 5.5× over |
| Nitrate Inorganic |
0.651 ppm | 0.14 | 10.0 | 11.3 | 11.3 | 10 | — | 4.7× over |
| Nitrate and nitrite Inorganic |
0.593 ppm | 0.14 | 10.0 | 11.3 | 11.3 | 10 | — | 4.2× over |
| Perfluoropentane sulfonic acid (PFPeS) PFAS |
1.34 ppt | 1.0 | — | — | — | — | — | 1.3× over |
| Dibromoacetic acid Disinfection byproduct |
0.0205 ppb | 0.03 | — | — | — | — | — | Below guideline |
| Chlorate Disinfection byproduct |
78.9 ppb | 210.0 | — | — | — | — | — | Below guideline |
| Manganese Heavy metal |
11.4 ppb | 100.0 | — | 50 | 80 | — | — | Below guideline |
| Vanadium Other |
1.03 ppb | 21.0 | — | — | — | — | — | Below guideline |
| Bromoform Disinfection byproduct |
0.00664 ppb | 0.5 | — | — | — | — | — | Below guideline |
| Monochloroacetic acid Disinfection byproduct |
0.334 ppb | 53.0 | — | — | — | — | — | Below guideline |
| Perfluorobutane sulfonate (PFBS) PFAS |
3.71 ppt | 2000.0 | — | — | — | — | — | Below guideline |
| Perfluoropentanoic Acid (PFPeA) PFAS |
1.15 ppt | 1000.0 | — | — | — | — | — | Below guideline |
| Perfluorohexanoic Acid (PFHxA) PFAS |
1.11 ppt | 1000.0 | — | — | — | — | — | Below guideline |
| Perfluorobutanoic Acid (PFBA) PFAS |
0.227 ppt | 1000.0 | — | — | — | — | — | Below guideline |
| Strontium Radiological |
0.0984 ppb | 1500.0 | — | — | — | — | — | Below guideline |
| Fluoride Inorganic |
0.138 ppm | — | 4.0 | 1.5 | 1.5 | — | — | Below guideline |
| PFOS + PFOA + PFHxS + PFNA PFAS |
27.5 ppt | — | — | 100 | 100 | 0.007 | — | Below guideline |
All values in the unit of the detected level. Red cells indicate the detected level exceeds that standard. Some contaminants have limits in some jurisdictions but not others (shown as —). The "Tested" column shows the year each contaminant sample was collected.
Sources: US EPA, EU Drinking Water Directive 2020/2184, WHO Guidelines, California OEHHA PHGs, EWG Tap Water Database.
Treatment plant contact info
For service issues, water quality concerns, or to request a Consumer Confidence Report from SAMMAMISH PLATEAU WATER & SEWER.