Is it illegal to block the sewer upstairs?

Break the law. According to Article 272 of the Civil Law of People's Republic of China (PRC), the owner has the right to possess, use, profit from and dispose of the exclusive part of his building. Owners shall not endanger the safety of buildings, damage the legitimate rights and interests of other owners, block sewers and affect the normal life of others when exercising their rights. This is a violation of the law, an illegal act and a crime. The blocked party may directly request the neighborhood committee to adjust or report to the police, or report to the court.