Is Sammamish, WA Tap Water Safe to Drink?
Sammamish tap water is legally compliant, but one contaminant exceeds health guidelines. Specifically: PFAS above EPA limits (PFOS: 6.95 ppt — limit is 4 ppt each). A point-of-use filter is recommended for drinking and cooking water.
Hardness Scale: Where Sammamish Falls
0Slightly
60Moderate
120Hard
180Very Hard
250Extreme
400+
How Sammamish Compares
Sammamish's water is 89% softer than the national average of 138 PPM - ranking in the bottom 96% for hardness nationwide. Most homes here do not need a softener. Within Washington, it ranks #23 of 26 cities (55% below the state average of 33 PPM). Among cities (50k-100k), Sammamish ranks #251 of 258 for hardness.
What Sammamish's Water Means for Your Home
Hardness: 15 PPM - Low Concern
Sammamish's water is soft at just 15 PPM. That's good news for your plumbing, appliances, and skin. Scale buildup is a non-issue here, and a water softener would be a waste of money. Sammamish is softer than 96% of US cities. If you're thinking about water treatment in Sammamish, contaminant filtration is the place to invest.
Contaminants & Safety
Forever chemicals (PFAS) are worth watching here. Sammamish has PFOS at 6.95 ppt, exceeding the EPA's 2024 limit of 4 ppt per compound. PFAS are synthetic compounds that accumulate in your body over time. A certified carbon filter or reverse osmosis system with NSF P473 certification is the most effective protection. See the regulatory timeline.
What's in the Treatment Process
Sammamish's surface water supply requires heavy chlorination to stay safe — but that creates a tradeoff. The treatment process generates disinfection byproducts: TTHMs at 17.8 ppb (22% of the legal limit, but 118x the EWG guideline) and HAA5 at 13.7 ppb (23% of the legal limit, but 137x the EWG guideline). These are within legal limits, but the EWG sets much tighter thresholds based on cancer-risk research. A whole-house activated carbon filter reduces both chlorine and byproducts.
Chromium-6 was detected at 0.109 ppb, which is 5.5x the EWG health guideline. There's no separate federal limit for chromium-6, only total chromium. A reverse osmosis system is the most effective removal method. All measurements are within federal legal limits. The EWG guidelines represent a more conservative, health-based standard.
| Contaminant | Detected | Health Guideline | Legal Limit | Status |
|---|---|---|---|---|
| Hardness (as CaCO₃) | 15 PPM | < 60 PPM | No federal limit | ✓ OK |
| Total Dissolved Solids | 27 PPM | < 300 PPM | 500 PPM | ✓ OK |
| PFAS (total) | 30.96 ppt | — | No total limit | Detected |
| ↳ PFOA | 0 ppt | 0 ppt | 4 ppt (2024) | ✓ OK |
| ↳ PFOS | 6.95 ppt | 0 ppt | 4 ppt (2024) | ⚠ Exceeds |
| Lead | 1.5 ppb | 0 ppb (no safe level) | 15 ppb (10 ppb in 2027) | ✓ Low |
| Chlorine / Chloramine | 0.4 mg/L | Taste threshold ~1.0 | 4.0 mg/L | ✓ Normal |
| Nitrate | 0.651 mg/L | 5 mg/L | 10 mg/L | ✓ OK |
Recommended Filter for Sammamish
PFAS exceed EPA limits (PFOS: 6.95 ppt — limit: 4 ppt each). A certified filter reduces these contaminants effectively.
How to Test Your Water in Sammamish
With PFAS at 30.96 ppt in Sammamish's supply, confirming your home's specific levels is especially important. PFAS vary by neighborhood and can concentrate differently depending on your position in the distribution system.
Free option: Request Seattle Public Utilities's annual Consumer Confidence Report for official city-level data.
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About Sammamish's Water Supply
Water Utility: Seattle Public Utilities
Water Source: Tolt River Watershed (Surface Water)
Population Served: 79,362
Hardness: 15 PPM (0.9 grains per gallon)
Sammamish's drinking water comes from surface sources — Tolt River Watershed. Surface water requires more extensive treatment than groundwater, including coagulation, filtration, and disinfection. This heavier chlorination is why disinfection byproducts tend to be higher in surface-supplied systems. On the upside, surface sources often deliver softer water than deep aquifers. The system serves 79,000 residents.
Water quality can vary by neighborhood and season. For your exact numbers, request Seattle Public Utilities's Consumer Confidence Report (CCR) or test your own tap.
ZIP Codes Covered by This Report
This water quality data applies to all areas served by Seattle Public Utilities in Sammamish, WA, including ZIP codes:
98014, 98019, 98024, 98027, 98029, 98045, 98050, 98065, 98068, 98074, 98075, 98224, 98256, 98288
If your ZIP code is listed above, this report covers your water supply. Water quality may vary slightly by neighborhood.
Compare Sammamish to Other Washington Cities
Frequently Asked Questions About Sammamish Water
Is Sammamish tap water safe to drink?
Where does Sammamish's water come from?
Do I need a water softener in Sammamish?
How do I remove PFAS from Sammamish tap water?
What water filter is best for Sammamish?
Is Sammamish water safe for babies and infants?
What are disinfection byproducts in Sammamish's water?
Is chromium-6 in Sammamish's water?
Data sources: Lead and copper data from EPA Safe Drinking Water Act LCR reporting. Contaminant data from utility-reported testing results. PFAS data from EPA UCMR5 (2023–2025). Hardness from USGS and municipal reports. Data reflects system-level testing results and may not match your specific tap due to neighborhood plumbing, season, or recent utility changes. For your utility's latest results, request their Consumer Confidence Report (CCR). Our methodology. Last updated: 2026-02-24.
What Sammamish Homeowners Actually Buy
Prioritized for contaminant reduction for homes with 15 PPM water and PFAS above EPA limits.
Affiliate disclosure: we may earn a commission. Selection based on Sammamish's water data.