Bathroom fixture
A toilet supply line can wet two suites from one fitting.
The small line behind a toilet is an easy miss. It can drip for days into the floor, or it can fail at the connection and send water to the ceiling below.
Look at the connection, not only the bowl.
A wet base can be a tank, a wax ring, or the supply stop. The supply line is the braided or plastic tube from the wall valve to the tank.
If the floor is wet only when the tank refills, the supply or fill valve is a likely place to start.
Shut the local stop if you can do it safely.
The small valve behind the toilet is meant for this. Turn it off and see whether the wetness stops. Do not keep flushing to ‘test’ it.
The suite below still needs a record.
Even a short spray can stain a ceiling and wet insulation. Tell the manager what you shut off and when the water stopped.
Questions people ask
Can I replace the supply line myself?
Only if you are allowed to work on that fixture and you can do it without opening walls. A leak that continues after the stop is closed needs a different look.
Why is the unit below wet if my floor looks dry?
Water can travel along the slab edge or the waste stack before it shows. The toilet is a suspect, not proof.