A catch basin is an underground tank found at many older Chicago homes, and yours could be filling with grease and sludge right now without any warning signs. Most homeowners never hear the term until a basement floor drain backs up or a plumber points one out in the yard.
Our licensed plumbers at Baethke have already measured, cleaned, and serviced 22 catch basins this year. We’ve seen what happens when a basin goes years without attention, and we’ve seen how simple it is to maintain once you know what to watch for.
In this guide, you’ll learn what a catch basin does, why so many Chicago homes have one, the signs that reveal when yours is full, how a proper cleaning works, and how it differs from a storm drain. By the end, you’ll know whether yours needs service and what to ask before you hire someone to clean it.
What Does a Catch Basin Do?
A catch basin is an underground tank on your property that collects wastewater from your kitchen sink and laundry, and in many older homes your downspouts, before it reaches your sewer line. Its job is to trap grease, solids, and sediment so they don’t clog your main sewer line or the city’s.
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Why Do So Many Older Chicago Homes Have Catch Basins?
Catch basins were commonly installed at both single-family and multifamily homes when much of Chicago was built in the late 1800s and early 1900s. Water from the kitchen, laundry, and often the downspouts flowed into the basin first. The basin held onto the heavy, messy material and let the water continue on to the sewer.
In the early 1900s, Chicago families cooked with a lot of lard and other heavy fats, and much of that grease went straight down the kitchen sink. At the same time, the city’s early sewer system wasn’t designed to handle it. All that grease and sediment could easily clog the city’s sewer lines.
To protect the sewers, catch basins were installed at individual homes. They acted as a first line of defense, collecting grease and solids on the property before the water reached the city main. Keeping the basin clean was the homeowner’s responsibility, and it still is today.
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How Does a Catch Basin Work?
A catch basin is designed to hold about 2 or 3 feet of standing water below its outlet pipe. That standing water is what makes it work.
As wastewater enters, grease and oils float to the top while heavier solids like food scraps, lint, and dirt sink to the bottom. The outlet pipe draws water from below the floating grease, so the cleaner water in the middle flows on to the sewer.
Over time, that layer of solids at the bottom keeps building. As it grows, there’s less room for water, and the basin can’t do its job as well.
How Often Does My Catch Basin Need to Be Cleaned?
Most Chicago homes need a catch basin cleaning every couple of years, with a quick inspection once a year to confirm the timing. Unfortunately, your catch basin doesn’t empty itself. Every bit of grease and sediment it catches stays there until it’s removed.
The good news is that most homes don’t need cleaning as often as they did decades ago, since we’re not pouring heavy fats down our sinks the way families once did. How often yours needs to be cleaned will depend on how much your kitchen and laundry are used.
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How to Tell if Your Catch Basin Is Full
Here are the most common signs that your catch basin is full, and ready to be serviced:
- Kitchen or laundry drains running slowly
- Water backing up through the basement floor drain or laundry tub
- Gurgling sounds when the washer drains
- A greasy or sewer odor near the basin or in the basement
- Backups that return soon after the drain line is rodded
The surest way to know is to measure it. We measure from the ground surface down to the top of the water, then measure how deep we can go before hitting the solids at the bottom.
A healthy basin should have about 2 to 3 feet of standing water between the surface of the water and the solids below. For example, say the water starts 50 inches below the ground. If we measure down and hit solids at 56 inches, there are only about 6 inches of water left. That basin is essentially full and needs to be pumped out. If there’s close to 3 feet of water, you still have time before it needs to be cleaned.
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How Is a Catch Basin Cleaned?
Not all catch basin cleanings are the same, and this is where it pays to ask questions.
“The best method uses a vacuum truck with a large-diameter hose and a spray nozzle,” says Josh, a licensed Baethke plumber with 25 years in the field. The crew vacuums out all the water and grease, sprays down the walls to remove chunks of grease stuck to the sides, then vacuums the basin all the way to the bottom.
Some companies only skim the grease off the top. That might look like a quick fix, but it leaves behind the heavy sediment at the bottom, including dirt from your downspouts and lint from your washing machine. Since that buildup is what takes up space in the basin, a skim-only cleaning doesn’t actually restore its capacity.
After a full cleaning, you don’t need to refill the basin. It naturally fills back up with water as soon as you start running the washing machine and doing dishes.
Also keep in mind, if we discover your sewer line is clogged while cleaning your catch basin, our plumbers can usually do a sewer line cleaning during the same visit.
What’s the Difference Between a Catch Basin and a Storm Drain?
These two are easy to confuse, but they do different jobs. A catch basin on your property collects wastewater from your kitchen sink and laundry. A storm drain at the curb collects rain and snowmelt from the street. Both usually end up in the same combined sewer in most of Chicago, and the City sometimes calls its street drains “catch basins” too, but only the one on your property is your responsibility.
Many homeowners choose to disconnect their downspouts from the catch basin and direct the water away from the house instead. That keeps extra rainwater and roof debris out of the basin. Make sure the water drains at least a few feet away from your foundation and doesn’t flow onto a neighbor’s property or the sidewalk.
Some people route their downspouts into a rain barrel. It’s a great way to collect reclaimed water for your lawn and garden instead of using fresh water from the house, and it’s an easy step toward a greener home.
Are Catch Basins Still Required in Chicago?
For most single-family homes, a catch basin is no longer required. Many older homes still have one, and as long as it’s there and connected, it needs regular maintenance.
Larger multifamily buildings are a different story. Because so many units drain into one line, catch basins are still required for buildings over six units. When there are over 6 units the building requires EITHER a catch basin, or individual grease traps under every kitchen sink.
Keep Your Catch Basin Working for You
A catch basin is one of those old Chicago plumbing features that works quietly for decades, as long as someone keeps it clean. Grease floats, solids settle, and each year the space for water gets a little smaller. A yearly measurement tells you where yours stands, and a full vacuum cleaning down to the floor of the basin brings it back to full capacity.
If you’ve never had yours looked at, you’re far from alone. Many homeowners we meet first learn about their catch basin the day a basement drain backs up. Getting ahead of it is easier on your home and your wallet.
Our plumbers will find your catch basin, measure it, and tell you honestly whether it needs cleaning now or can wait another year. When it’s time, we clean it the right way, walls and all, so you’re not paying for a skim job that leaves the real problem behind.
Call Baethke Plumbing at or schedule your catch basin inspection online. We serve homes and buildings across many Chicago neighborhoods such as Lincoln Park, Logan Square, and Portage Park, and the nearby suburbs, including Evanston, Oak Park, and Skokie.
Questions About Chicago Catch Basins Answered
What is a catch basin?
A catch basin is an underground tank on your property that collects wastewater from your kitchen sink and laundry, and in many older homes your downspouts, before it reaches your sewer line. It traps grease, solids, and sediment so they don’t clog your sewer line or the city’s.
How often does a catch basin need to be cleaned?
Most Chicago homes need a catch basin cleaning every couple of years, depending on how much the kitchen and laundry are used. A yearly inspection tells you whether it’s time for a cleaning or whether you can wait.
How do I know if my catch basin is full?
Common signs include slow kitchen or laundry drains, water backing up through the basement floor drain, gurgling when the washer drains, and grease or sewer odors. The surest way to know is to measure it: a healthy basin has about 3 feet of standing water above the solids, and a basin with only a few inches left needs to be pumped out.
