Who will take care of pouring dirty water from upstairs to downstairs?

You can call the property and ask them to adjust. If the newly bought building is generally a property problem, you can negotiate with the upstairs first. It should be his responsibility, and sometimes the responsibility of the property. Of course, it is best to find the property three parties to solve the problem together. After all, there are many opportunities for cooperation in the future, but we should not be too soft. On the whole, it should not make you pay attention to cooperation. That's my answer. If you still don't understand, you can ask me questions.