The city of São Paulo has 11,451,245 inhabitants and is the largest state capital in Brazil, according to the IBGE Census (2022). Its metropolitan region has about 22 million inhabitants, but there are still many areas with informal urban occupation, not legally authorized by municipal governments. In the capital of the State of São Paulo alone, there are about one million inhabitants in these areas of unplanned urban occupation, that is, informal settlement. Providing sanitation services has been a major challenge, not only because it depends on the regularization of the ownership of these areas, many of which are invaded, but also as a sanitation engineering solution. Techniques are needed that go beyond the usual Brazilian engineering standards. Two real cases are presented here: the implementation of a sanitary sewage collection network in the Pinheiros River Basin and a rainwater drainage solution in Jardim Piratininga. Both occupations are in the municipality of São Paulo, but the sewage treatment plant is located downstream in the metropolitan municipality of Barueri, which receives sewage from a large part of the city. The organized participation of the population was fundamental in making it possible in both cases to install both the sewage collection network in the Pinheiros River Basin and the rainwater drainage system in Jardim Piratininga. The contracting process of the works and their unit costs are also briefly presented. The photo shows an example of informal occupation next to a canal that forms part of the Tietê river, the largest that runs through the São Paulo Metropolitan Region.