The ground area surrounding a home can only accommodate so much rainwater. When there is too much rain, water overloads the city sewer system and causes a backup in one’s basement. The city should take responsibility when backups involve the city sewer system. City sewer backups are normally detected after a flood. Drain system is a complex piping system and should be only installed by a licensed professional. If your property drains system has been poorly installed or repaired pipe can fail causing blockages and backups.