The SFD describes all of the excreta flows across the city or town, and through all stages of the sanitation service chain. This includes:
- Wastewater from households and institutions which is commonly made up of blackwater, grey water and run off and includes sewage flowing in sewers
- Faecal sludge from onsite sanitation systems
- Excreta deposited directly into the environment via open defecation
- Effluent or supernatant that leaves onsite sanitation systems after solid separation
- Infiltrate, including effluent (or overflow) from onsite sanitation systems that is absorbed by the ground, or discharged.