Chicago Water Quality Guide

Chicago draws its drinking water from Lake Michigan, the third-largest Great Lake and one of the largest freshwater lakes in the world. The lake provides an abundant, high-quality source of water for the city's approximately 2.7 million residents, plus millions more in surrounding suburbs.

The City's Water System

Source Water Quality

Lake Michigan provides excellent source water quality. The lake's vast size provides natural dilution of contaminants, and Chicago's intake pipes extend far into the lake to draw cleaner, deeper water. The Department of Water Management conducts over 200,000 water quality tests annually to ensure safety.

Treatment Process

Chicago's water undergoes comprehensive treatment at two state-of-the-art facilities:

1. Screening: Removes large debris and aquatic life
2. Coagulation: Chemicals bind small particles together
3. Sedimentation: Particles settle out in basins
4. Filtration: Water passes through sand and gravel filters
5. Disinfection: Chlorine kills harmful microorganisms
6. Fluoridation: Fluoride added for dental health
7. Corrosion Control: Blended phosphate added to reduce lead leaching

While Chicago's source water and treatment are excellent, the city faces a significant challenge: it has more lead service lines than any other U.S. city. An estimated 400,000 lead service lines connect homes to water mains throughout Chicago, a legacy of building codes that actually required lead pipes until 1986.

How Lead Gets into Chicago Water

Lead doesn't come from Lake Michigan or the city's water treatment plants. It leaches from the lead service lines connecting individual homes to the water main, and potentially from lead solder, brass fixtures, or galvanized pipes inside homes. Factors that increase lead leaching include:

• Water sitting in pipes overnight or during work hours
• Hot water (which dissolves more lead than cold)
• Disturbances from construction, water main breaks, or meter work
• New lead pipes or recently disturbed pipes (protective scale is disrupted)

City's Response

Chicago has implemented several measures to address lead concerns:

• Corrosion Control: Blended phosphate is added to water to create a protective coating inside pipes, reducing lead leaching
• Free Water Testing: The city offers free lead testing kits to residents
• Filter Distribution: Free NSF 53 certified water filters available at select locations
• Lead Service Line Replacement Program: Pilot programs underway, with federal infrastructure funding enabling expanded replacement

However, full replacement of 400,000 lead service lines will take decades and cost billions of dollars. In the meantime, individual action remains essential.

Lead Testing Results

Chicago's water system meets the EPA's Lead and Copper Rule requirements, with 90th percentile lead levels below the federal action level of 15 parts per billion (ppb). However, it's important to understand what this means:

Other Contaminants

Beyond lead, Chicago water quality monitoring includes:

• Disinfection Byproducts: Total trihalomethanes (TTHMs) and haloacetic acids form when chlorine reacts with organic matter. Levels are monitored and typically compliant but can fluctuate.
• PFAS ("Forever Chemicals"): Emerging contaminants of concern. The EPA has set new standards; testing is ongoing.
• Chromium-6: No federal limit exists, but this contaminant has been detected in Chicago water at low levels.
• Microorganisms: E. coli and coliform bacteria are routinely tested; Chicago's treatment effectively controls these.

Construction and Water Main Work

Construction activity, water main repairs, and even meter replacement can disturb lead service lines and cause temporary spikes in lead levels. The city recommends flushing water and using filters after any work on water infrastructure near your home.

Testing your own water is the only way to know what's coming out of your tap. Chicago offers free testing, and private options provide more comprehensive analysis.

Free Testing from the City

Private Laboratory Testing

For comprehensive testing including multiple contaminants:

• Illinois EPA Certified Labs: Find certified laboratories at the Illinois EPA website
• Tap Score: Mail-in testing with detailed analysis ($100-300)
• National Testing Laboratories: Comprehensive water panel testing

How to Collect a Proper Sample

1. Use the cold water tap you most often use for drinking (typically kitchen)
2. Let water sit in pipes for at least 6 hours (overnight is ideal)
3. Do NOT run water before collecting the sample
4. Fill the sample bottle according to instructions
5. Consider collecting both a "first draw" sample and a sample after 2-3 minutes of flushing to compare

Interpreting Results

• Non-detect or under 1 ppb: Excellent; minimal lead present
• 1-5 ppb: Low but detectable; consider filtration for young children or pregnant women
• 5-15 ppb: Moderate concern; use NSF 53 certified filter
• Above 15 ppb: Exceeds EPA action level; use bottled or filtered water, contact city
• Above 40 ppb: Significant concern; do not use for drinking or cooking without filtration

Immediate Steps Everyone Should Take

For Households with Young Children

Children under 6 are most vulnerable to lead exposure. Additional precautions include:

• Use filtered or bottled water for drinking and formula preparation
• Have children tested for blood lead levels by their pediatrician
• Ensure dietary calcium and iron, which help reduce lead absorption
• Be extra vigilant about flushing after water sits in pipes

Filtration Options

Important: The city distributes free NSF 53 certified pitcher filters at select locations. Check chicago.gov/water for distribution sites.

Lead Service Line Replacement

Full replacement of your lead service line is the only permanent solution. Options include:

• City Program: Chicago is expanding its replacement program with federal infrastructure funds. Check eligibility at the city website.
• Private Replacement: Homeowners can pay to replace their portion of the service line ($5,000-15,000+), but partial replacement can temporarily increase lead levels.
• Full-Line Replacement: Both the homeowner's portion and the city's portion should ideally be replaced together for best results.

Renters

If you rent in Chicago, you still have options:

• Request lead testing through the city's free program
• Ask your landlord about the building's service line and plumbing
• Use an NSF 53 certified filter for drinking water
• Illinois law requires landlords to disclose known lead hazards
• Building owners with 6+ units may be required to test and disclose lead levels

Schools and Daycares

Illinois now requires testing in schools and licensed daycares. Results must be made available to parents. If your child's facility hasn't been tested or results aren't available, advocate for testing or consider sending filtered water with your child.

Suburban Residents

Many Chicago suburbs receive Lake Michigan water through the city or regional water authorities. Lead concerns depend on your local infrastructure. Contact your water utility for service line information and testing resources.