The creation of the geometric network in the Update module fails. A message appears: [...] Table already exists [...] An object named [...] already exists in the database.
During the previous deletion of the geometric network not all network system tables in the DB were deleted.
For example, the following tables visible in SQL Server Management Studio were left over from ELE_NET:
In SQL Server Management Studio delete these files and also remove the corresponding entries from the dbo.SDE_table_registry table.
Afterwards, the creation of the geometric network with the Update Module works properly again.
This workaround is certainly the fastest, but strictly speaking it is not recommended.
It would be cleaner to rebuild the SDE DB and copy the data into it.