Estimated data about population connected in case of sewage system for 2014 are given according to changed estimation method. In 1995-2001, data about population using the network are presented for cities by name, and the layout: urban gminas contains data for urban gminas, whereas the layout: urban-rural gminas contains data for urban parts of some urban-rural gminas. In 2002, the source of data are the results of the National Census 2002. The lack of information about the length of the active network in the report for 2002-2004 is caused by the fact that at the moment of the census, the dwelling was fitted with a sewage system but this network was actually managed by a local community (a group of inhabitants), i.e. its own water intake and its own network. This concerns especially rural areas. According to the information gathered about these areas, in the following years there will be a gradual takeover (buy-out) of these systems by water authorities and they will be managed or administrated by the units whose statutory activity is water supply. The length of the active distribution network: - which is in the municipality's management or administration, it is the municipal offices and municipal self-government organizational units with the ownership form 113, ie the ownership of local government units or self-government legal persons; - operated by municipal economy units, it is municipal self-government organizational units with ownership form 113, ie ownership of local government units or self-government legal persons (in the Act on local self-government, Article 18 paragraph 2 point 9 letter f) and h), it says that the commune council may create companies, cooperatives, enterprises, plants and other communal organizational units). Other distribution companies, cooperatives, universities, independent public healthcare institutions, associations, research institutes and other entities conducting activity in the field of water supply and / or sewage disposal, which is a predominant or secondary activity, will be responsible for the remaining distribution network. Data on population using the sewage supply system at municipal level was compiled on the basis of information from the following statistical reports: M-06 – Report on water supply network and sewage network – within the scope of the number of sewage supply connections to residential buildings, and collective accommodation buildings; SG-01 part 3 – Statistics of municipality: housing and municipal economy – regarding the number of residential buildings with a connection to the sewage supply system; and information from the TERYT register, and the Balance of dwelling stocks, the basis of which are data from the National Population and Housing Census, in the scope of the following indicators; number of dwellings per one building, number of persons per one dwelling. In order to ensure data consistency, the percentage of the total population using water supply system, sewage system, or gas supply system was calculated using data originating from Census 2011. Since 2020 these indicators was calculated using data from Census 2021.