Where is the water coming from?
Basement water tells a different story depending on where it shows up — Chicago’s combined sewers and high water table cause very different problems. Tap a spot to see what it is, the most likely source, and how it’s fixed.
Tap a marker to trace the leak.
Pick any numbered spot to see what it is, where the water is most likely coming from, and the right next step. Not sure? Start wherever you first noticed water or an odor.
1 Window well
What it means The recessed area around a below-grade basement window, usually with gravel and a drain at the bottom to carry off rain.
Likely source Surface water, not groundwater — a clogged window-well drain, overflowing gutters or downspouts, poor grading, or a missing well cover letting rain pool against the glass.
What to do Clear the well drain, redirect downspouts away from it, fix grading that slopes toward the house, and add a fitted cover.
Window well drains & exterior drainage →2 Wall-floor (cove) joint
What it means The seam where your foundation wall meets the concrete floor — one of the most common places for groundwater to push into a basement.
Likely source Hydrostatic pressure: groundwater forced up through the joint. But the soil saturation driving it is often fed by surface water (downspouts, grading, window wells), not a truly high water table — usually a drainage problem, not a plumbing one.
What to do Don’t just patch it from inside — have the perimeter assessed so surface-drainage causes are ruled out before committing to interior drain tile and a sump that relieves the pressure.
Interior drainage & foundation waterproofing →3 Floor drain
What it means The grated drain in the basement floor. In most Chicago basements it ties directly into the (often combined) sewer; in some re-plumbed homes it drains to a sump or ejector pit instead.
Likely source Dirty water bubbling up from it is the first sign of a sewer backup — usually when heavy rain surcharges the combined sewer (the real problem is the sewer line). If it instead drains slowly or pools, that’s a clog or dried-out trap, not a surcharge.
What to do If dirty water rises from the drain, stop using water and treat it as a sewer backup. For slow draining, the drain or its trap likely needs clearing.
Sump pump vs check valve vs overhead sewer →4 Ejector pit
What it means A sealed, vented basin with an ejector pump that lifts wastewater from below-grade fixtures — a basement bathroom or laundry — up into the sewer. It is not part of your groundwater system.
Likely source Water or odor here is a sewage issue, not groundwater — a failed ejector pump, a bad check valve, or a broken lid seal or vent. It can also back up when the sewer it pumps into is surcharged or blocked, and should never overflow under normal use.
What to do Have the ejector pump, check valve, and sealed lid serviced — and never treat it like a sump pit.
Sewage ejector pump service →5 Sump pit
What it means A lined basin in the floor that collects groundwater from the drain tile around your foundation. The sump pump sits in it and pushes that water back outside.
Likely source A rising level is normal groundwater, but a pit that overflows, runs constantly, or floods the floor around it usually means the pump has failed, lost power, can’t keep up with the water table in heavy rain, or has a stuck float or clogged intake.
What to do Test that the pump runs, confirm it’s sized right, and add a battery backup. Most pumps last about 7–10 years. If the pump runs fine but water keeps returning, the problem is the discharge line.
Sump pump installation & backup systems →6 Discharge line
What it means The pipe that carries clean pump water from your sump out and away from the foundation — never wastewater. It’s the sump system’s exit, not a drain.
Likely source If water pools by the house and re-enters the pit, the outlet is too close to the foundation or poorly sloped. If water never leaves the pit, the line is frozen, clogged, or disconnected.
What to do Keep the line clear, sloped away, and discharging several feet from the house; in winter, watch for ice at the outlet.
Sump discharge & exterior drainage →7 Sewer line
What it means The buried main drain that carries all your home’s wastewater out to the city — not your sump water. In much of Chicago it connects to a combined sewer that also carries stormwater.
Likely source Backups happen when heavy rain overwhelms the combined sewer and pushes wastewater back toward below-grade drains. They can also come from a blockage in your own lateral — tree roots, grease, or collapsed clay tile — which a camera inspection tells apart from a city-side surcharge.
What to do For city-side surcharge, the fix is flood-control protection — compare a backwater valve against an overhead sewer. A blockage in your own lateral has to be cleared or repaired first.
Sump pump vs check valve vs overhead sewer →Still not sure where it’s coming from? We’ll inspect it, identify the likely source, and explain what actually fixes it — a guide, not a diagnosis.