Products are materials that are also called ‘wastes’ or ‘resources’. Some products are generated directly by humans (e.g. urine and faeces), others are required in the functioning of technologies (e.g. flushwater to move excreta through sewers) and some are generated as a function of storage or treatment (e.g. Sludge). For the design of a robust sanitation system, it is necessary to define all of the products that are flowing into (inputs) and out of (outputs) each of the sanitation technologies in the system. The products referenced within this text are described below.