When water is standing around a basement floor drain, it is easy to assume the floor drain itself is clogged. Sometimes that is true. Other times, the floor drain is only where the backup shows up, while the real blockage is in the main sewer line.
Why the symptoms can look the same
Floor drains often tie into the same system as laundry tubs, kitchen lines, bathroom drains, and the main sewer line. If the main line is blocked, water from other fixtures can come up through the lowest opening, which is often the floor drain.
How the real cause is diagnosed
A drain technician looks at which fixtures are affected, what happens when water is run elsewhere, and where the cleanout access is. When needed, a camera inspection can confirm whether the problem is in the floor drain branch or farther down the main line.
Why the answer matters
Cleaning the wrong section can make the problem come back. The goal is to clear the line where the blockage actually is, then test the drain so you know it is flowing before the job is done.