Summer Storms and the "Combined Sewer" Problem
In Chicago, we live for summer. We endure the "Chiberia" months just for those glorious days on the lake, street festivals, and patio dining. But there is one part of a Chicago summer that is significantly less poetic: the sudden, sky-opening flash flood.
If you’ve lived in the city or the surrounding suburbs for a while, you’ve likely noticed that a heavy 30-minute downpour can lead to flooded viaducts and, unfortunately, flooded basements. This isn’t just a matter of "too much rain"—it’s a direct result of Chicago’s unique, historic, and often overwhelmed combined sewer system.
Understanding how this system works is the first step in defending your home against the "summer surge."
What Exactly is a "Combined Sewer"?
In many modern cities, there are two separate sets of underground pipes: one for stormwater (rain) and one for sanitary sewage (from your toilets and sinks).
Chicago, however, is an older city. Much of our infrastructure relies on a combined system. This means that the water running off your roof and the street goes into the exact same pipe as the wastewater from your bathroom.
Normally, this works fine. All that water travels together to a treatment plant. But during a classic Chicago summer "gulley washer," the volume of rainwater can be tens of thousands of gallons per minute. When that massive influx hits the system, the pipes reach capacity. When the main city line is full, the water has nowhere left to go but back up the "lateral" lines—the pipes that connect your home to the street.
The result? Wastewater and rainwater surge into your basement through floor drains and low-lying fixtures.
Why Summer Storms are the Primary Threat
Unlike a slow spring thaw, summer storms in the Midwest are often "flash" events. We get an incredible amount of water in a very short window of time.
The ground in Chicago can also be quite clay-heavy, which doesn't absorb water quickly. When the soil is saturated or the rain is falling too fast for the earth to soak it up, all that water immediately heads for the sewer. This "shock" to the system is what causes the pressure to build, leading to that dreaded gurgling sound in your basement floor drain.
Your Defensive Playbook: Long-Term Solutions
If you’re tired of crossing your fingers every time the sky turns grey, there are professional plumbing solutions designed specifically for Chicago’s combined sewer challenges.
1. Backwater Valves
A backwater valve is a "one-way street" for your plumbing. It is installed on your main sewer line and features a flap that allows water to flow out of your house but automatically closes if water tries to surge back in from the city main.
2. Overhead Plumbing
This is considered the "gold standard" for basement protection. Overhead plumbing involves rerouting your basement sewage to a ejector pump, which lifts the waste to a higher point before it exits the house. This effectively raises the "exit point" of your plumbing above the level of the city sewer main, making it physically impossible for the city's overflow to gravity-flow back into your basement.
3. Deep-Cleaning Your Lines
Sometimes, the system is struggling because your own private line is restricted. Years of "summer grease" or root intrusion can narrow your pipes. When the city main is under pressure, a restricted line is the first to fail. A professional hydro-jetting session can ensure your pipes are at their full capacity to handle the load.
Stay High and Dry This Summer
You can’t control the Chicago weather, but you can control how your home responds to it. Whether you need an emergency inspection after a backup or you want to discuss permanent solutions like a backwater valve, our team is ready to help.
Don’t wait for the next storm cloud to appear on the horizon. To protect your basement and give yourself peace of mind during the next "Big One," contact Angel Sewer & Plumbing today for a professional consultation.
