595.000 km is the total length of the German sewer network.
By the way, in Germany there are mainly three different types of sewer networks: Mixed water (~250.000 km) , rainwater (~125.000 km) and sewage water (~220.000 km).
Source: https://de.dwa.de/files/_media/content/03_THEMEN/Entwaesserungssysteme/Kanalumfrage/Zustand-der-Kanalisation-2020.pdf