A floor drain can become the place where a downstream problem becomes visible.
Because floor drains are often low points in a drainage system, water can appear there when flow cannot continue normally downstream. The significance changes depending on what else is happening in the property.
Pay attention to whether the floor drain reacts when a toilet is flushed, a washing machine drains, or several fixtures are used. If wastewater is actively backing up, reduce unnecessary water use until the problem can be evaluated.
If a floor drain backs up at the same time as toilets, tubs or other drains, the shared branch or main sewer line becomes more important to evaluate than the floor drain alone.
What information helps?
Note which fixtures are affected, what happens immediately before the symptom, whether another fixture reacts at the same time, and whether the problem has happened before. Those details can help a drain professional choose an appropriate next step without asking you to diagnose the system yourself.