Improvements in sanitation provision, and in particular options for collection and treatment of sewage, are critical requirements to reduce health and environmental risks to populations in rapidly-urbanising informal settlements. This paper presents a novel technique to evaluate the costs of different sewage treatment-transportation options based on the spatial and topological properties of different networks. This is made possible using crowd-sourced, open spatial data-sets which allow us to simulate different sanitation network scenarios within a geospatial software environment, and ascertain the long term operational costs of different network configurations. It is envisaged that such a tool could be used by engineers as part of the sanitation planning process to evaluate sanitation network implementation options, as such we include a case-study example based on the Kibera settlement in Kenya.