User interface explains the type of toilet construction—pedestal, pan or urinal—with which a user comes in contact; it is the way in which the user accesses the sanitation system. In most of the cases, the choice of the user interface depends on the availability of land and water and, also sociocultural factors. Only excreta and black/yellow water and wash water originate at the user interface, and not grey water (grey water is generated from domestic sources).