Step 1: The lake

Chicago's report notes that Lake Michigan is the only Great Lake entirely within the United States, and the second largest by volume, at 1,180 cubic miles of water.

Step 2: Two giant treatment plants

The City of Chicago treats the water at two plants: the Jardine Water Purification Plant — which the City calls the largest conventional water treatment plant in the world — and the Eugene Sawyer Water Purification Plant. Together they can produce about 2.1 billion gallons a day. Per Chicago's report, Jardine serves the northern parts of the city and suburbs, and Sawyer serves the southern parts.

Step 3: Tunnels, pumps, and mains

The City says its system includes 65 miles of tunnels, 12 pumping stations, and 4,300 miles of water mains, and it supplies more than five million people in Northeastern Illinois — including Oak Lawn.

Step 4: Oak Lawn's own system

From there, the Village of Oak Lawn delivers the water through its own pipes and monitors chlorine levels so the water stays disinfected on the way. That's why Oak Lawn publishes its own water quality report, with its own lead and chlorine by-product results.

Step 5: The last few feet

The final stretch — your service line, your home's pipes, solder, and faucets — is where lead most often gets in. The lake and the plant aren't the issue; the plumbing can be. Oak Lawn's filing with the Illinois EPA lists 2,214 lead service lines out of 17,039 connections, and the Village plans to replace about 2,300 lead and galvanized lines over five years starting in 2026.

A few numbers from Chicago's 2025 report

  • Chlorine: 1 ppm (limit 4 ppm)
  • Fluoride: 0.75 ppm, added to promote strong teeth
  • Sodium: 9.10 ppm, from naturally occurring deposits
  • PFAS: Chicago reports non-detect results in its 2014, 2020, and 2024 studies

These are Chicago system numbers. Oak Lawn's own results, measured in its own pipes, are on the Oak Lawn report card.

Quick questions

Where does Oak Lawn's water come from?

Lake Michigan water treated by the City of Chicago and purchased through the Oak Lawn Regional Water System; the Village maintains chlorine in its distribution system.

Sources

  1. Village of Oak Lawn 2024 Annual Drinking Water Quality Report — Village of Oak Lawn
  2. Suburban Customers & Regional Partnerships — City of Chicago Department of Water Management
  3. 2025 Water Quality Report — City of Chicago Department of Water Management
  4. PFAS Findings — City of Chicago Department of Water Management

This guide is general information, not medical or legal advice. Oak Lawn Water Filtration is an independent business and is not affiliated with the Village of Oak Lawn. Product certifications are model-specific and can change; check the current listing before you buy.