In 1998, in both a national and international move, dictated by the orientations of the World Bank, the public sanitation of Rabat-Salé transferred from public town administration to private management. An european private company was put in charge of sanitation services. In 2000 and 2001, I developed an ethnographic study on work on the sewages. The public apparatus constructed in the different neigh-borhoods confirms that the distances between inhabitants and wastes vary greatly from one sector of the city to the other. This observations show how notions of soil and contamination regarding excremental matters result in classifications of the individuals. Bodies and social positions are correlatively constructed, according to the institutional hierarchy. It’s the same mechanism for workers. Excremental substances have a political effect. An anthropological approach to urban wastes and their corresponding techniques provides an understanding of construction mechanism or legitimization of social positions in this context of privatization.