Is Lake Oswego, OR Tap Water Safe to Drink?
Yes, Lake Oswego tap water is safe to drink. Hardness is low at 18 PPM, and no contaminants exceed health guidelines. Most homes here don't need treatment.
Hardness Scale: Where Lake Oswego Falls
0Slightly
60Moderate
120Hard
180Very Hard
250Extreme
400+
How Lake Oswego Compares
Lake Oswego's water is 87% softer than the national average of 138 PPM - ranking in the bottom 94% for hardness nationwide. Most homes here do not need a softener. Within Oregon, it ranks #36 of 48 cities (28% below the state average of 25 PPM). Among smaller cities, Lake Oswego ranks #265 of 288 for hardness.
What Lake Oswego's Water Means for Your Home
Hardness: 18 PPM - Low Concern
Lake Oswego's water is slightly hard at 18 PPM. Most households won't notice any issues at this level. Scale buildup is minimal, and a water softener would be overkill. Lake Oswego is softer than 94% of US cities. If you're thinking about water treatment, contaminant filtration is where to focus your money, not softening.
Contaminants & Safety
Disinfection byproducts are the notable finding here. Lake Oswego's water has TTHMs at 8.3 ppb and HAA5 at 3.99 ppb — both within legal limits, but the EWG health guidelines are far stricter. These byproducts form when chlorine reacts with organic matter during treatment. A whole-house activated carbon filter reduces both chlorine and its byproducts. Want the full picture? Request your utility's annual Consumer Confidence Report.
What's in the Treatment Process
Lake Oswego's surface water supply requires heavy chlorination to stay safe — but that creates a tradeoff. The treatment process generates disinfection byproducts: TTHMs at 8.3 ppb (10% of the legal limit, but 55x the EWG guideline) and HAA5 at 3.99 ppb (7% of the legal limit, but 40x 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 0.0925 ppb, which is 4.6x 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) | 18 PPM | < 60 PPM | No federal limit | ✓ OK |
| Total Dissolved Solids | 32 PPM | < 300 PPM | 500 PPM | ✓ OK |
| PFAS (total) | 0 ppt | — | No total limit | ✓ ND |
| ↳ PFOA | 0 ppt | 0 ppt | 4 ppt (2024) | ✓ OK |
| ↳ PFOS | 0 ppt | 0 ppt | 4 ppt (2024) | ✓ OK |
| Lead | 1.5 ppb | 0 ppb (no safe level) | 15 ppb (10 ppb in 2027) | ✓ Low |
| Chlorine / Chloramine | 0.5 mg/L | Taste threshold ~1.0 | 4.0 mg/L | ✓ Normal |
| Nitrate | 0.28 mg/L | 5 mg/L | 10 mg/L | ✓ OK |
Good news for Lake Oswego residents. Your water quality is generally good. Most homes in this area do not need a water softener. If you have concerns about lead (especially in buildings constructed before 1986) or chlorine taste, a point-of-use filter is the most practical and cost-effective solution.
How to Test Your Water in Lake Oswego
City-wide data is a solid starting point, but your specific tap might differ based on plumbing age, distance from the treatment plant, or seasonal changes.
Free option: Request Lake Oswego Municipal Water's annual Consumer Confidence Report for official city-level data.
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About Lake Oswego's Water Supply
Water Utility: Lake Oswego Municipal Water
Water Source: Clackamas River (Surface Water)
Population Served: 40,000
Hardness: 18 PPM (1.1 grains per gallon)
Lake Oswego's drinking water comes from surface sources — Clackamas River. 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 40,000 residents.
Water quality can vary by neighborhood and season. For your exact numbers, request Lake Oswego Municipal Water'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 Lake Oswego Municipal Water in Lake Oswego, OR, including ZIP codes:
97034, 97035, 97036
If your ZIP code is listed above, this report covers your water supply. Water quality may vary slightly by neighborhood.
Compare Lake Oswego to Other Oregon Cities
Frequently Asked Questions About Lake Oswego Water
Is Lake Oswego tap water safe to drink?
Where does Lake Oswego's water come from?
Do I need a water softener in Lake Oswego?
What are disinfection byproducts in Lake Oswego's water?
Is chromium-6 in Lake Oswego's water?
Can I drink Lake Oswego tap water straight from the faucet?
What water filter is best for Lake Oswego?
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.