Whether you flush it down the toilet, wash it down the sink, or mop it down the floor drain, it all leads to the same public sewer system.
The plumbing lines from your home or apartment building drain by gravity into the public sewer main.
From there the wastewater flows by gravity until it reaches a pumping station.
A pumping station lies at a low point in the collection system usually with multiple public sewer mains draining to it.
At that point, wastewater must be pumped to a point of higher elevation where it can begin gravity flowing to the next pumping station before ultimately reaching the Des Moines Metropolitan Wastewater Reclamation Facility though pipes as large as 12 feet in diameter.
To find out what happens to the wastewater once it reaches the treatment facility, visit the Plant Process page.