Sewer rate principle

Sewer rate is decided by a principle in Japan.
The principle is that sanitary sewage cost shall be borne by users while storm water by the public.
Cost bearing by the public means input of general tax.

Therefore, sewer management is paid by a combination of user charge and general tax.
In some cases of combined sewer, the cost is allocated to users and general tax by the design flow.
The flow of storm water is much greater than that of sanitary sewer.
Therefore, municipalities with more combined sewers receive more money from general tax than those with only sanitary sewers.