In the 1840s, the older half of Hamburg, Germany, burned. When that area was rebuilt, a totally new sewer system was designed (by W. Lindley, a distinguished English engineer) and built. It was vented through the roof drains of the connected buildings, and a flushing system was created (once per week utilizing tide water) to clean the new main line sewers. This new design philosophy for the sewering of a major metropolitan area was soon recognized as the model, and, thereafter, was utilized by other cities (in Europe and the United States).
See Tracking Down the Roots of Our Sanitary Sewers for more information.
S. Sorensen, B. Petersen, N. Kofod, Pl Jacobsen, Historical Overview of the Copenhagen sewerage system, from IWAP Online, accessed September 2007.