Downstairs always say that my house is leaking, but my house can't find the leakage point at all. I suspect this is her own house. Please help me analyze it, thank you.

Your sewer main runs through the floor to the ceiling of his house. Generally everyone will make a ceiling for beauty. If his house has a ceiling, you can't see the pipes. It is suspected that there is a loose pipe joint here. His family can see it as long as they take apart the ceiling. Generally, it is a problem of engineering quality. They can ask the property to repair it. Your family is not responsible for this pipeline, but they have to cooperate with the maintenance.