Plumbing in Chicago runs through clay laterals under the alley, galvanized stacks in the walls, and basements that sit below the street. A backup at a garden-level floor drain after a hard rain is the lateral or the catch basin until proven otherwise. A pinhole in an old stack shows up later as a bubble in the plaster. Radiator leaks get mistaken for pipe leaks because the water appears in the same chase. Say what metal you can see.
Ejector pits fail at the float or the check, and the lid tells you when the pump quit. Know if you even have a pit before you describe the flood. A hose bib on masonry splits when the hose stays on through a freeze. If the main shutoff spins and does not close, say so, because that changes the first step. Look at the radiator valve before you call a drip a supply leak.
A two-flat often backs up at the lower sink while the upper one still drains. That pattern is grease in the shared stack. A laundry on an old floor drain can overload a line that was never asked to take it. Roots from the parkway tree enter at clay joints. Say where the cleanout is, basement or alley, and whether anyone has already opened it.
Water quality and old galvanized together explain weak hot water at a second-floor bath. The heater may be fine while the lines are not. A leak on your side of a parkway meter pit still belongs in the call. Shut water off if a tank or a split pipe is actively flooding, and say that you did. Winter is when unused garden-unit sinks freeze at an exterior wall; say if that unit was left unheated.
Lead with backup, burst, no hot water, or a drain that returns into the lower unit. Name alley, stack, or heater. Say if a radiator is the thing actually dripping. Chicago clay and old pipe do not improve overnight. Call the number on this page.