Is Sammamish, WA Tap Water Safe to Drink?
Graded C- — but Copper, Manganese and 1 more were detected above EPA limits. Here's what's in the water and how to remove it. What to do next ↓
56/100
waterverge.com Sammamish, WA — Water Quality Report
Sammamish's drinking water received a grade of C- (56 out of 100), indicating poor water quality. The city's 3 water systems serve approximately 88,043 residents using purchased surface water.
Lead levels were measured at 1.7 ppb (90th percentile), well within EPA limits. UCMR 5 testing detected 6 PFAS compounds, with levels exceeding EPA maximum contaminant levels in the water supply.
The system has 433 violations on record, including 6 health-based violations. 10 remain unresolved.
What to know about Sammamish's water
Sammamish ranks #197 out of 294 cities in Washington for water quality, placing it below average in the state.
The city draws from surface water sources, which are more susceptible to seasonal runoff and agricultural contamination, requiring extensive multi-barrier treatment including coagulation, filtration, and disinfection.
Of particular concern: PFAS "forever chemical" levels exceed the 2024 EPA maximum contaminant levels. These synthetic compounds don't break down naturally and require specialized filtration such as reverse osmosis or granular activated carbon.
Hexavalent chromium (chromium-6) was detected at 0.58 µg/L in UCMR 3 testing. While below California's 10 µg/L limit and with no federal MCL set, residents sensitive to this contaminant may consider reverse osmosis filtration.
Water quality score
See methodology →Is Sammamish, WA water safe to drink?
Sammamish's drinking water has significant quality concerns based on EPA testing data. With a grade of C- (56/100), the system has issues across multiple categories. A water filter is recommended for all residents. The city's 3 water systems serve approximately 88,043 residents using surface water (rivers, lakes, or reservoirs).
Recent water quality updates for Sammamish
A timeline of significant water quality events, violations, and data updates.
PFAS levels exceed EPA maximum contaminant levels. Reverse osmosis or activated carbon filtration recommended.
Latest EPA compliance and testing data incorporated into Sammamish's water quality assessment. Grade: C- (56/100).
Federal disaster declaration (FEMA DR-3629). Flood event — may have impacted local water infrastructure.
Contaminants: Consumer Confidence Rule.
Contaminants: Revised Total Coliform Rule.
Contaminants: Nitrate.
Key contaminant findings
Based on the most recent EPA sampling data for Sammamish's water supply.
Well within EPA limits.
Exceeds EPA action level. Copper can leach from household plumbing — flush taps for 30 seconds before drinking.
PFAS "forever chemicals" exceed EPA maximum contaminant levels. Reverse osmosis or granular activated carbon filtration strongly recommended.
PFAS "forever chemicals" detected
UCMR 5 testing found 6 PFAS compounds in Sammamish's water supply. PFAS are synthetic chemicals that persist indefinitely in the environment and the human body.
Violation history
Sammamish's water system has 433 total violations on record, including 6 health-based violations. 10 remain unresolved. 4 violations were issued in the last 5 years.
Flood & environmental risk
King County has experienced 10 federally declared disasters since 1990. Flooding and severe storms can overwhelm water treatment plants, cause sewage overflows, and introduce agricultural runoff, bacteria, and sediment into drinking water supplies. Local water sources include Issaquah Creek, Sammamish Lake, Raging River, Snoqualmie River.
Where does Sammamish's water come from?
Sammamish's drinking water comes from surface water (rivers, lakes, or reservoirs), supplied by 3 water systems serving approximately 88,043 people. Surface water sources are more susceptible to contamination from runoff, industrial discharge, and algal blooms, requiring extensive treatment. Nearby water bodies include Issaquah Creek (river), Sammamish Lake (lake), Raging River (river), Snoqualmie River (river).
What Sammamish residents can do
Recommended: Reverse osmosis system. This addresses the specific contaminants found in Sammamish's water.
Your water utility is required to publish an annual Consumer Confidence Report (CCR) with detailed testing results. Ask for the latest copy or check your utility's website.
Sammamish's area has a history of flooding. After severe weather, watch for boil water advisories from your local utility.
Data: EPA SDWIS, UCMR 5 (PFAS), FEMA, NOAA. Last updated May 2026.
Top contaminants to know
View all ↓Forever chemicals overview
National PFAS report →Violation summary
Violations & advisories
Top industrial polluters within 10 miles of Sammamish
Industrial polluters nearby
Reported releases to surface water by facilities near Sammamish, ranked by pounds discharged annually.
Total reported releases to surface water: 2 lbs
| Facility | Top chemical | To surface water (lbs/yr) | Distance |
|---|---|---|---|
TEREX WASHINGTON SOUTH CAMPUS REDMOND, WA98052 | Certain glycol ethers | 2 | 5.4 mi |
PRINTED CIRCUITS ASSEMBLY CORP BELLEVUE, WA98005 | — | — | 5.9 mi |
DARIGOLD - ISSAQUAH ISSAQUAH, WA98027 | — | — | 4.0 mi |
WESTERN PNEUMATIC TUBE CO LLC KIRKLAND, WA98033 | — | — | 9.0 mi |
Source: EPA Toxic Release Inventory (TRI) 2023
Superfund sites within 10 miles of Sammamish
Superfund sites nearby
Federally tracked hazardous-waste sites on the EPA National Priorities List. Proximity does not necessarily indicate tap-water contamination — the connection depends on hydrology and treatment.
- QUENDALL TERMINALS8.6 mi
- QUEEN CITY FARMS10.0 mi
Source: EPA Superfund National Priorities List
Flood & disaster history
King County has experienced 10 federally declared disasters since 1990. Flooding and severe weather can compromise water treatment infrastructure and introduce contaminants into drinking water supplies.
Recommended water filters
Based on contaminants detected in Sammamish's water supply, we recommend the following filter types.
Full contaminants report
| Contaminant | Detected Level | EPA Limit | Unit | Category | Status |
|---|---|---|---|---|---|
| Lead (90th percentile) LeadHeavy Metal A toxic heavy metal that can leach into drinking water from older pipes, solder, and fixtures. No amount of lead in water is considered safe. Health EffectsBrain and nervous system damage in children, kidney damage, high blood pressure, and reproductive problems in adults. EPA Limit15 ppb action level Common SourcesCorrosion of lead pipes, lead solder, brass faucets, and household plumbing. | 1.7 | 15 | ppb | Inorganic | Safe |
| Copper (90th percentile) CopperInorganic A metal that enters drinking water mainly through corrosion of copper plumbing. Small amounts are essential for health, but excess levels are harmful. Health EffectsGastrointestinal distress (nausea, vomiting, diarrhea) at short-term high levels; liver and kidney damage from long-term exposure. EPA Limit1.3 mg/L action level Common SourcesCorrosion of copper household plumbing, erosion of natural deposits. | 3.80 | 1.3 | mg/L | Inorganic | Over Limit |
| 11Cl-PF3OUdS | ND | HI | µg/L | PFAS | Not Detected |
| 4:2 FTS | ND | HI | µg/L | PFAS | Not Detected |
| 6:2 FTS 6:2 FTSPFAS A fluorotelomer sulfonate commonly found at sites contaminated with aqueous film-forming foam (AFFF) used in firefighting. Health EffectsPotential liver toxicity and endocrine disruption. Less studied but identified as a contaminant of concern. EPA LimitNo individual MCL (not yet regulated) Common SourcesFirefighting foam (AFFF), airports, military bases, and industrial facilities. | ND | HI | µg/L | PFAS | Not Detected |
| 8:2 FTS | ND | HI | µg/L | PFAS | Not Detected |
| 9Cl-PF3ONS | ND | HI | µg/L | PFAS | Not Detected |
| ADONA | ND | HI | µg/L | PFAS | Not Detected |
| HFPO-DA HFPO-DA (GenX)PFAS A replacement for PFOA in manufacturing, marketed as safer but still a persistent "forever chemical." Also known as GenX. Health EffectsLiver and kidney effects, reproductive toxicity, immune system effects, and potential cancer risk. EPA Limit10 ppt MCL Common SourcesFluoropolymer manufacturing (used as PFOA replacement), industrial wastewater discharge. | ND | 0.01 | µg/L | PFAS | Not Detected |
| lithium LithiumInorganic A naturally occurring alkali metal found in groundwater. Monitored under UCMR 5 to assess occurrence in drinking water. Health EffectsKidney effects at high doses. Low-level exposure effects under study; some research suggests neurological effects. EPA LimitNo MCL (monitoring only under UCMR 5) Common SourcesNatural mineral deposits, geothermal water, and industrial discharge. | ND | HI | µg/L | PFAS | Not Detected |
| NEtFOSAA | ND | HI | µg/L | PFAS | Not Detected |
| NFDHA | ND | HI | µg/L | PFAS | Not Detected |
| NMeFOSAA | ND | HI | µg/L | PFAS | Not Detected |
| PFBA PFBAPFAS One of the shortest-chain PFAS compounds. Very mobile in water and difficult to remove with standard filtration. Health EffectsThyroid effects, potential developmental toxicity. Shorter half-life in body than long-chain PFAS. EPA LimitNo individual MCL (not yet regulated) Common SourcesDegradation of longer-chain PFAS, industrial discharge, and firefighting foam. | ND | HI | µg/L | PFAS | Not Detected |
| PFBS PFBSPFAS A short-chain PFAS used as a replacement for PFOS. While it clears the body faster than long-chain PFAS, it still persists in the environment. Health EffectsThyroid effects, reproductive and developmental toxicity, kidney effects. EPA LimitPart of Hazard Index (1.0) Common SourcesIndustrial discharge, firefighting foam, and as a replacement chemical in manufacturing. | 0.009 | HI | µg/L | PFAS | Detected |
| PFDA | ND | HI | µg/L | PFAS | Not Detected |
| PFDoA | ND | HI | µg/L | PFAS | Not Detected |
| PFEESA | ND | HI | µg/L | PFAS | Not Detected |
| PFHpA PFHpAPFAS A medium-chain PFAS compound found in various environmental samples. Less studied than PFOA/PFOS but still considered a contaminant of concern. Health EffectsLiver effects, potential developmental toxicity, and endocrine disruption. EPA LimitPart of Hazard Index (1.0) Common SourcesDegradation of longer-chain PFAS, industrial discharge, and contaminated water sources. | ND | HI | µg/L | PFAS | Not Detected |
| PFHpS | ND | HI | µg/L | PFAS | Not Detected |
| PFHxA PFHxAPFAS A short-chain PFAS replacement chemical widely used after manufacturers phased out longer-chain PFAS. Very commonly detected in water. Health EffectsLiver and kidney effects, potential thyroid disruption. Considered less toxic than long-chain PFAS but still persistent. EPA LimitNo individual MCL (not yet regulated) Common SourcesIndustrial processes, firefighting foam (AFFF), food packaging, and textile treatment. | 0.004 | HI | µg/L | PFAS | Detected |
| PFHxS PFHxSPFAS A medium-chain PFAS found in firefighting foam and consumer products. It has a long half-life in the human body, similar to long-chain PFAS. Health EffectsImmune system effects, thyroid disruption, and potential reproductive and developmental harm. EPA LimitPart of Hazard Index (1.0) Common SourcesFirefighting foam (AFFF), waterproof textiles, food packaging, and industrial discharge. | 0.017 | HI | µg/L | PFAS | Detected |
| PFMBA | ND | HI | µg/L | PFAS | Not Detected |
| PFMPA | ND | HI | µg/L | PFAS | Not Detected |
| PFNA PFNAPFAS A long-chain PFAS compound used in manufacturing fluoropolymers. It bioaccumulates in the body and is very persistent in the environment. Health EffectsDevelopmental effects, liver toxicity, immune suppression, and potential cancer risk. EPA LimitPart of Hazard Index (1.0) Common SourcesFluoropolymer manufacturing, industrial emissions, and contaminated water sources. | ND | HI | µg/L | PFAS | Not Detected |
| PFOA PFOAPFAS A long-chain PFAS ("forever chemical") once widely used in nonstick coatings and firefighting foam. It persists in the body and environment for years. Health EffectsLinked to kidney and testicular cancer, thyroid disease, elevated cholesterol, and reproductive issues. EPA Limit4.0 ppt MCL Common SourcesIndustrial discharge, firefighting foam (AFFF), nonstick cookware manufacturing, and contaminated groundwater. | ND | 0.004 | µg/L | PFAS | Not Detected |
| PFOS PFOSPFAS A long-chain PFAS compound historically used in stain-resistant coatings and firefighting foam. One of the most studied and persistent PFAS chemicals. Health EffectsLiver damage, immune system suppression, thyroid disruption, increased cholesterol, and potential cancer risk. EPA Limit4.0 ppt MCL Common SourcesFirefighting foam (AFFF), industrial sites, stain-resistant fabric treatments, and contaminated groundwater. | 0.011 | 0.004 | µg/L | PFAS | Over MCL |
| PFPeA PFPeAPFAS A short-chain PFAS compound commonly detected in drinking water. One of the most frequently found PFAS in UCMR 5 monitoring. Health EffectsLess studied than PFOA/PFOS. Potential liver and thyroid effects. Research is ongoing. EPA LimitNo individual MCL (not yet regulated) Common SourcesIndustrial discharge, firefighting foam degradation, and consumer products. | 0.004 | HI | µg/L | PFAS | Detected |
| PFPeS | 0.004 | HI | µg/L | PFAS | Detected |
| PFTA | ND | HI | µg/L | PFAS | Not Detected |
| PFTrDA | ND | HI | µg/L | PFAS | Not Detected |
| PFUnA | ND | HI | µg/L | PFAS | Not Detected |
Lead level trend (90th percentile)
Copper level trend (90th percentile)
See how Sammamish compares by contaminant
Explore where Sammamish ranks among all Washington cities for specific contaminants.
Water source & infrastructure
Where Sammamish's water comes from
Sammamish's drinking water comes primarily from surface water sources such as rivers, lakes, or reservoirs.
Surface water systems require multi-stage treatment including coagulation, sedimentation, filtration, and disinfection to meet EPA Safe Drinking Water Act standards.
These sources can be impacted by seasonal changes, stormwater runoff, upstream agriculture, and industrial discharge.
The system is operated by local government ownership and serves approximately 88,043 people through 3 water systems.
Water bodies near Sammamish
Sammamish is located near 4 notable water bodies. As a surface water system, these water bodies may directly influence the city's drinking water supply.
Water systems serving Sammamish
| System Name | PWSID | Population | Source |
|---|---|---|---|
| SAMMAMISH PLATEAU WATER & SEWER | WA5340900 | 79,362 | SWP |
| NE SAMMAMISH SEWER & WATER DISTRICT | WA5375265 | 8,516 | GW |
| MAYFIELD RV PARK | WA5311154 | 165 | GW |
How Sammamish compares
Full Washington rankings →Sammamish's score of 56/100 is on par with the average of 53/100 among major Washington cities. It outscores 7 of 10 nearby cities.
Nearby cities
View Washington rankings →About Sammamish, WA
Wikipedia →Sammamish is a city in King County, Washington, United States. The population was 67,455 at the 2020 census. Located on a plateau, the city is bordered by Lake Sammamish to the west and the Snoqualmie Valley to the east. Sammamish is situated 20 miles east of Seattle, is a member of the Eastside, and is a part of the Seattle metropolitan area.
Learn more about your water
Guides and resources related to Sammamish's water quality findings.
Explore water quality across King
Frequently asked questions
Is Sammamish, WA tap water safe to drink?
Sammamish's water quality earned a grade of C- (56/100). Significant issues have been found. A water filter is strongly recommended. The city ranks #197 out of 294 cities tested in Washington.
What contaminants are in Sammamish's water?
Lead was measured at 1.7 ppb (90th percentile). 6 PFAS compounds were detected. 433 violations are on record.
How is Sammamish's water quality grade calculated?
The grade is based on four factors: violation history (40%), lead and copper levels (25%), PFAS contamination (25%), and regulatory compliance (10%). The score is also adjusted based on how complete the available data is. See our methodology page for full details.
Do I need a water filter in Sammamish?
PFAS compounds exceed EPA limits — a reverse osmosis or activated carbon filter is recommended.
Where does Sammamish's water come from?
Sammamish's water is sourced from Purchased surface water. The city has 3 water systems serving approximately 88,043 residents.
What health violations has Sammamish's water system had?
Sammamish has 6 health-based violations on record. The most recent violation was recorded in July 2023. Health-based violations mean the water exceeded EPA maximum contaminant levels (MCLs) for a regulated substance. 10 violations remain unresolved.
Why does Sammamish have so many PFAS compounds in its water?
6 different PFAS "forever chemical" compounds were detected in Sammamish's water supply during UCMR 5 testing. PFAS contamination often originates from proximity to military installations (AFFF firefighting foam), airports, industrial manufacturing sites, or wastewater treatment facilities. Some levels exceed the 2024 EPA maximum contaminant levels — a reverse osmosis or NSF-certified activated carbon filter is strongly recommended.
How does Sammamish's water compare to other cities?
Sammamish ranks #197 out of 294 cities in Washington (better than 33% of state cities) and #12486 out of 15744 cities nationally (21th percentile). The grade of C- reflects the combined assessment of violation history, lead and copper levels, PFAS contamination, and regulatory compliance.