Water Quality in Lake Oswego, OR: 10 Violations — Grade A
Grade A · Score 86/100 · 5 water systems · Updated 2026-05-03
Lake Oswego's water meets all EPA standards with no health-based violations.
Data: EPA Safe Drinking Water Information System (SDWIS) Last verified: 2026-05-03
EPA files for Lake Oswego, OR document 10 water violations — a record that encompasses health-based exceedances, monitoring and reporting failures, and any other compliance events registered for local public water systems across all available federal compliance records for this area.
Water Quality by ZIP Code in Lake Oswego
Water quality varies across Lake Oswego's 2 ZIP codes. Check your specific ZIP for detailed contaminant data.
| ZIP Code | Grade | Score | Violations | Health | |
|---|---|---|---|---|---|
| 97034 | B | 83 | 5 | 0 | View report → |
| 97035 | A | 88 | 5 | 0 | View report → |
Water Quality Overview
Lake Oswego, Oregon receives a water quality grade of A with an overall score of 86 out of 100, based on EPA compliance data from the Safe Drinking Water Information System (SDWIS).
The 5 water systems serving Lake Oswego have accumulated 10 EPA violations (all monitoring/reporting type). These violations are tracked across 2 ZIP codes serving approximately 47,650 people.
What Grade A Means
A grade of A indicates excellent compliance with EPA drinking water standards. Lake Oswego's water systems have maintained strong performance in both contaminant monitoring and regulatory compliance.
Lead Levels
The average 90th percentile lead level across Lake Oswego water systems is 0.0015 mg/L — within EPA limits. No ZIP codes exceed the EPA lead action level.
With 63% of homes built before 1986, Lake Oswego has a higher-than-average risk of lead from older plumbing. Lead solder was banned in 1986, and homes built before this date may have lead in pipes, solder joints, or fixtures.
Water Systems Serving Lake Oswego
Lake Oswego is served by 5 community water systems regulated under the Safe Drinking Water Act. These systems collectively serve approximately 47,650 people across 2 ZIP codes.
Each water system is identified by a Public Water System ID (PWSID) and is required to:
- Test for over 90 regulated contaminants on a regular schedule
- Report results to the EPA and state regulators
- Issue an annual Consumer Confidence Report (CCR) to all customers
- Take corrective action when violations occur
The EPA has taken 20 enforcement actions against water systems serving Lake Oswego. Enforcement actions range from informal compliance assistance to formal orders and penalties.
How to Check Your Water in Lake Oswego
Enter your ZIP code on ZipCheckup to see your specific water system data, including contaminant levels, violation history, and safety scores
Request your CCR — your water utility must provide an annual Consumer Confidence Report with detailed test results for all monitored contaminants
Get a home test — certified kits cost $20–$50 and test for lead, bacteria, and common contaminants. Professional lab tests ($150–$400) cover a broader panel
Consider filtration — NSF-certified filters can remove specific contaminants. Reverse osmosis removes the broadest range; activated carbon is effective for chlorine and many organics
Check for advisories — monitor your local utility website and local news for boil water advisories or system alerts
Contaminants Detected in Lake Oswego Water Systems
The following contaminants have been detected or caused violations across Lake Oswego's water systems:
| Contaminant | Category | MCL | Violations | ZIPs Affected | Health-Based |
|---|---|---|---|---|---|
| Surface Water Treatment Rule | Treatment Technique | N/A | 8 | 2 | No |
| Stage 1 DBP Rule | Treatment Technique | N/A | 2 | 2 | No |
MCL = Maximum Contaminant Level (EPA enforceable standard). Health-based violations indicate levels that may pose direct health risks.
EPA Enforcement History
The EPA and state regulators have taken 10 enforcement actions against water systems serving Lake Oswego. Recent actions:
| Date | Action Type |
|---|---|
| 2025-09-02 | State Order Extension |
| 2025-08-22 | State Order Extension |
| 2024-12-12 | State Informal Action |
| 2024-11-14 | State Order Extension |
| 2024-07-24 | State Order Extension |
| 2024-07-03 | State Order Extension |
| 2024-02-05 | State Order Extension |
| 2023-07-24 | State Order Extension |
| 2023-07-17 | State Order Extension |
| 2022-10-26 | State Order Extension |
Enforcement actions range from informal compliance assistance to formal orders and penalties. The most recent action was on 2025-09-02.
Lake Oswego vs. Nearby Oregon Cities
How Lake Oswego's water quality compares to similar cities in Oregon:
| City | Grade | Violations | Systems | Population |
|---|---|---|---|---|
| Lake Oswego | A | 10 | 5 | 47,650 |
| Roseburg | B | 20 | 5 | 45,740 |
| Happy Valley | A | 9 | 5 | 50,170 |
| Clackamas | A | 6 | 5 | 50,761 |
Common Questions About Lake Oswego Water
These are the most common questions residents search for about water quality in Lake Oswego, Oregon:
Is Lake Oswego water hard or soft? Water hardness varies by source. Lake Oswego's 5 water systems use multiple sources. Check your ZIP code report for specific hardness data.
Can I drink Lake Oswego tap water? Lake Oswego's water receives a grade of A (86/100). No health-based violations have been recorded, but home testing is always recommended.
What is the best water filter for Lake Oswego? A NSF/ANSI 53-certified filter for lead removal is a good general choice. See our Water Filter Matcher for personalized recommendations.
Lake Oswego vs. Oregon Average
Understanding how Lake Oswego compares to the broader Oregon average helps contextualize your local water quality. Factors like water source, treatment methods, and infrastructure age all contribute to differences between cities in the same state.
To see how individual neighborhoods compare, check the ZIP code reports below — water quality can vary significantly even within Lake Oswego.
ZIP Codes in Lake Oswego
Lake Oswego spans 2 ZIP codes. The ZIP with the lowest water quality score is 97034. Each ZIP code has its own water quality profile based on the specific water system serving that area. Check each ZIP code for detailed contaminant data, violation history, and system information.
Data Sources
- Water quality: EPA Safe Drinking Water Information System (SDWIS)
- Lead/copper: EPA Lead and Copper Rule sampling data
- Radon: EPA Map of Radon Zones
- Enforcement: EPA ECHO database
- Filter recommendations: NSF/ANSI certified products
Updated daily.
Frequently Asked Questions
Your Water is Safe — Here's How to Keep It That Way
Grade A is excellent news. Here's what proactive homeowners do to maintain water quality:
Annual Water Testing
EPA recommends annual testing even with clean water. Home test kits: $20-$50. Catches changes before they become problems.
Maintenance Filtration
A basic carbon filter removes chlorine taste and catches emerging contaminants like PFAS that aren't yet fully regulated.
Plumbing Check
Even safe city water picks up lead from home pipes. If your home was built before 1986, a one-time pipe inspection is recommended.