In cities of the Global South, faecal sludge management (FSM) has arisen as an acceptable and economical alternative for managing excreta. Shit flow diagram (SFD) has emerged as the preferred tool for the planning and advocacy of FSM services. Besides context-specific challenges, FSM planning, especially the use of SFD is impeded by the lack of data related to on-site sanitation systems (OSSs) and lack of capacity at the local level. This paper sets out to demonstrate how the capacity-building approach can be extended to overcome these two challenges in planning FSM with a substantial share of the information collected through household surveys. We argue that even the resource-constrained towns in the Global South have access to college students, smartphones and open source applications and demonstrate how they can be harnessed to collect the data in a cost-effective manner. Using the data collected by 150+ university students, participants of a summer school, we prepare a SFD for Alleppey, a town in Kerala, India. We argue such repeated exercises by subsequent batches of students can help understand local problems, arrive at context specific solutions and monitor them to instill better accountability of local governments. We also identify two issues with the current SFD preparation process and find it is necessary to contextualise the output of the tool to use it for planning. We suggest that the methods demonstrated here be incorporated in the future refinements to the SFD tool to make it more useful for planning city-wide FSM services.