Water Quality in Lake Oswego, OR: 49 Violations Recorded for Mapped Water Systems
7 water systems · 2 directly mapped ZIP records
Available EPA records report 49 violations across 2 directly mapped ZIP records with known counts for Lake Oswego. This is compliance evidence, not a property-level tap-water verdict.
Data: EPA Safe Drinking Water Information System (SDWIS)
Water Quality by ZIP Code in Lake Oswego
This table shows typed EPA water evidence only. Missing violation counts are displayed as N/A, not zero.
| ZIP Code | Violations | Health | |
|---|---|---|---|
| 97035 | 41 | 1 | View report → |
| 97034 | 37 | 0 | View report → |
Water Quality Overview
Lake Oswego, Oregon has directly mapped EPA water-system data for 2 ZIP codes. This page reports typed compliance facts and does not relabel the multi-source Home Safety Score as a drinking-water grade.
The available EPA records report 49 violations, including 1 health-based violation across 2 directly mapped ZIP records with reported counts.
Lead Levels
The average of the reported 90th-percentile lead results across the ZIP codes of Lake Oswego is reported as 0 mg/L (a reported 0 is not proof of no lead; check the source record for its reporting limit); the EPA action level of 0.015 mg/L applies to a water system's own 90th-percentile result and is not a safety threshold (EPA's health goal for lead is zero). No exceedances appear among the 2 ZIP records with known lead status.
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 7 community water systems regulated under the Safe Drinking Water Act. About 46,994 people live in the area (2 ZIP codes, Census); this is not the systems' reported service population.
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
EPA records list 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 and violation history
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 |
|---|---|---|---|---|---|
| Consumer Confidence Rule | Reporting | N/A | 14 | 2 | No |
| Xylenes, Total | Organic | N/A | 3 | 2 | No |
| Lead and Copper Rule | Treatment Technique | N/A | 3 | 2 | No |
| Di(2-ethylhexyl) phthalate | Organic | 0.006 mg/L | 2 | 2 | No |
| 1,2,4-Trichlorobenzene | Organic | N/A | 2 | 2 | No |
| cis-1,2-Dichloroethylene | Organic | N/A | 2 | 2 | No |
| Dichloromethane | Organic | N/A | 2 | 2 | No |
| o-Dichlorobenzene | Organic | N/A | 2 | 2 | No |
| p-Dichlorobenzene | Organic | N/A | 2 | 2 | No |
| Vinyl chloride | Organic | N/A | 2 | 2 | No |
| 1,1-Dichloroethylene | Organic | N/A | 2 | 2 | No |
| trans-1,2-Dichloroethylene | Organic | N/A | 2 | 2 | No |
| 1,2-Dichloroethane | Organic | N/A | 2 | 2 | No |
| 1,1,1-Trichloroethane | Organic | N/A | 2 | 2 | No |
| Carbon tetrachloride | Organic | N/A | 2 | 2 | No |
The standard column shows the EPA Maximum Contaminant Level (MCL) except for lead and copper, whose value is an action level that triggers corrective steps and is not an MCL. Health-based violations are MCL, MRDL and treatment-technique violations.
EPA Enforcement History
The EPA and state regulators have taken enforcement actions against water systems serving Lake Oswego. Recent actions:
| Date | Action Type |
|---|---|
| 2026-02-16 | State Order Extension |
| 2025-10-03 | State Order Extension |
| 2025-09-02 | State Order Extension |
| 2025-05-09 | State Order Extension |
| 2025-04-07 | State Order Extension |
| 2025-03-12 | State Order Extension |
| 2025-03-10 | State Informal Enforcement |
| 2024-12-12 | State Informal Action |
| 2024-11-16 | State Order Extension |
| 2024-11-14 | State Order Extension |
Enforcement actions range from informal compliance assistance to formal orders and penalties. The most recent action was on 2026-02-16.
Lake Oswego vs. Nearby Oregon Cities
How Lake Oswego's water quality compares to similar cities in Oregon:
| City | Direct EPA ZIPs | Violations | Systems | Population |
|---|---|---|---|---|
| Lake Oswego | 2 | 49 | 7 | 46,994 |
| Redmond | 1 | 5 | 5 | 44,287 |
| Roseburg | 2 | 14 | 6 | 51,390 |
| Klamath Falls | 2 | 204 | 3 | 54,963 |
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 7 water systems use multiple sources. Check your ZIP code report for specific hardness data.
Can I drink Lake Oswego tap water? City-level EPA records cannot determine safety at a specific tap. The measured subset contains 1 health-based violation; check the affected utility record and consider certified testing.
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. EPA water-system coverage is available for 2 directly mapped ZIP codes. 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
Source reporting periods vary. See each cited source for its publication schedule.