The inadequate provision of sanitation in informal urban settlements, also known as slums, continues to be an important issue. New technologies and services are being designed to solve this problem. However, the history of failed sanitation programmes and projects highlights a lack of understanding of how slum inhabitants decide on investing in such products and services. In this paper, we gather perspectives from potential clients and investigate how slum inhabitants (1) perceive the current situation and whether they desire improvements of sanitation, (2) how they evaluate a new toilet that is still in development, and how (3) social processes and (4) constraints affect decisions. Data were collected through interviewing 1538 people within a general household survey. People using shared and public latrines desire an improvement of their sanitation facilities. The lack of water for washing is perceived by residents as a the biggest problem when accessing current latrines. The new toilet was mostly evaluated positively: people like it, expect large health benefits from it and it complies with cultural norms. However, people also expect some problems with the functioning of the toilet and expect opposition to pay for the service, due to the high costs and a lack of space to set up new toilets.