Many older Chicago buildings send their drains through a private catch basin before anything reaches the street. It’s a chamber near the house, often brick, where kitchen grease, sand and grit are meant to settle out ahead of the lateral. When it fills, the drains slow, the yard can pool around downspouts that run into it, and backups return however often the line gets rodded. Call Chicago Plumbworks for catch basin cleaning and we’ll book a licensed plumber to pump it out and check the pipe beyond it. That visit is also the time to ask about an overhead sewer, the bigger fix for sewage coming up the floor drain every time it storms.
What does a catch basin do?
It gives the heavy and greasy stuff a place to stop. Wastewater runs in near the top, the chamber stays full of standing water, and the outlet to the street leaves well above the floor of the basin. Grease floats up and hardens into a cap, sand and grit sink to the bottom, and the water in between flows on to the lateral. The basin keeps working until the grease and the silt meet the outlet.
In buildings that have one, the kitchen line is often what feeds it, since grease is what the basin is there to catch. On older property the roof downspouts may run into it as well, because older City code had downspouts piped into the house drain. Some buildings were put up without a basin and drain straight to the sewer.
The grate at the curb isn’t yours
The City calls its street inlets catch basins too. Those are the grates along the curb and in the alley, and the Department of Water Management cleans them on its own schedule. Catch basins all over town hold a plastic restrictor the City calls a Rain Blocker. It meters storm water into the sewer slowly and leaves the street ponded for three or four hours on purpose, so the water waits in the street instead of in basements. A basin on your property is a separate structure, and by the City’s rules, cleaning it is the owner’s job.
How do you know the catch basin is full?
The clearest sign is a backup that keeps coming back. Watch for these:
- Rodding clears it for a while, then the same drain backs up again. A cable through a basin packed with grease cuts a path and leaves the rest of the grease where it was.
- The kitchen sink slows first. If the kitchen line feeds the basin, it’s the first drain to feel a full one.
- Water stands at or above the inlet pipes when the lid comes off. In a working basin it sits below them.
- Water pools around a downspout that goes into the ground, or around the lid itself, when it rains.
- A sewer smell hangs around the lid in the yard or gangway.
- The floor drain backs up on a dry day, with no storm to blame.
How often should a catch basin be cleaned?
There’s no set calendar, because how fast a basin fills depends on what drains into it. These shorten the interval:
- More kitchens. Each one adds grease, so a basin behind a three-flat fills faster than the one behind a bungalow.
- Downspouts tied in, especially under trees, since leaves and roof grit wash in with every storm.
- A garbage disposal on the kitchen line, which sends food solids along with the grease.
- Years since anyone pumped it.
The first cleaning sets the schedule. The plumber sees how thick the grease cap was and how deep the silt ran, and from that you can judge how long it took to fill. Good times to have it opened: when you buy the building, and any time a line that feeds it gets rodded.
What happens on a cleaning visit?
The plumber lifts the lid and pumps the basin out: the grease cap, the standing water and the silt on the bottom. Then the inlet and outlet pipes and the walls of the basin get a look for cracks, loose brick or roots.
The water level in the basin also tells the plumber which way to look. Water backed up over the inlet pipes means the basin or the pipe just past it is blocked. A normal level with slow drains inside means the clog is upstream, somewhere in the building’s own pipes, and the basin may only need a routine cleaning. If the drains are still slow once it’s clean, the next step is to rod and camera the line from the basin to the street, since the trouble may sit farther out.
What is an overhead sewer?
An overhead sewer takes every basement drain off the gravity line to the street. The floor drain, the basement toilet, the laundry tub and the shower all empty into a sealed ejector pit instead. A pump lifts that water to a pipe hung near the basement ceiling, which joins the building’s drain on its way out. Upstairs fixtures keep draining down by gravity, the same as before. The old gravity connection under the basement floor gets cut and capped, so nothing down there has an open path to the street, and a full sewer can’t push back in.
Some buildings get a partial version, sometimes called a modified overhead sewer, where the basement fixtures go to an ejector that pumps into the existing stack. If that’s the plan, ask what it leaves connected below the floor.
The trade-off is the pump. FEMA and the Village of Palatine both describe the plumbing changes as the costlier fix, and Palatine points out that the pumps stop in a power outage. So the pump an overhead system needs, its alarm and its backup power deserve as much thought as the piping.
When does an overhead sewer conversion make sense?
When the basement has to stay dry every time and one flap valve is too much to bet on. Palatine’s guidance names a big investment in a finished basement as the case for it.
| Your basement | Backwater valve | Overhead sewer |
|---|---|---|
| Unfinished, storage only, backed up once | The usual first step | More than it needs |
| Finished or lived in, backed up before | If the flap sticks open, the room floods | The stronger pick |
| Floor far below the street, fixtures down there | Works as long as it seals | Takes the basement off the street sewer |
| Two-flat on one shared building drain | Holds back the upstairs units too while closed | Upstairs keeps draining by gravity |
| Power out during a storm | Still closes, no power needed | Pit fills until the pump runs again |
Overhead sewers in two-flats and three-flats
The conversion protects the garden unit without changing how the flats upstairs drain. With a tenant downstairs, put the pit alarm where it can be heard inside the unit and keep the pit lid sealed. Then make sure the tenant knows to stop using the unit’s fixtures and call when the alarm goes off.
What goes into a conversion?
The visit starts with a survey of the building: which fixtures and floor drains sit below grade, where a pit can go, and where the overhead line can leave the building. The work then means opening the floor to set the pit and cap the old connection, and running the basement drains to the pit. The new line gets hung near the ceiling and tied into the building drain, and the pump, check valve and alarm get tested.
The price moves with the number of fixtures and floor drains below grade, the finished floors and walls in the way, and how far the pit sits from where the line leaves. The condition of the old lateral counts too, along with any backup power or alarm added on the same job.
Backing up for a different reason?
- It’s coming up now and can’t wait for a booked visit
- Only one sink or toilet won’t go down, and the rest of the house drains fine
- The camera found a collapsed section past the basin