General Questions

A Shit Flow Diagram (SFD) is an easy-to-understand advocacy and decision-support tool comprising a report (SFD Report) which contains a graphic (SFD Graphic). An SFD summarises service outcomes in terms of the flow and fate of excreta in urban areas. It includes a qualitative assessment of the context in which service delivery takes place and a complete record of data sources. The process of developing the report is as important as the report itself. Use of the SFD method enables a standardised assessment of excreta flows in urban areas. Due to the sensitivity around the term "shit", the following terms are often used interchangeably: Excreta Flow Diagram or Faecal Waste Flow Diagram. 

The SFD Graphic indicates where the problems lie in an urban area, but without understanding the local context you cannot understand why these situations occur. The SFD Report will help to answer questions such as “why is only half of the excreta produced onsite collected?” or “why is only half of the wastewater that reaches the treatment facilities treated?” The SFD Report provides information on the institutional frameworks, roles and responsibilities, regulatory aspects, and other issues that directly or indirectly impact the provision of sustainable sanitation services. It also includes the assumptions used to prepare the SFD Graphic.

The SFD Graphic is a visual representation that enables stakeholders to identify service outcomes in terms of the flow and fate of excreta produced by the population. Excreta which is safely managed and move along the sanitation service chain are represented by green arrows moving from left to right in the graphic, while excreta which are unsafely managed are represented by red arrows. Unsafely managed flows discharging to the environment are represented by red arrows turning towards the bottom of the graphic. The width of each arrow is proportional to the percentage of the population whose excreta contribute to that flow. 

The point at which the arrows drop down to the bottom of the graphic, gives a general indication of how far the excreta have travelled from the initial population centre. For example, open defecation normally occurs in the ‘local area’ close to where people live, whereas untreated wastewater in open drains or sewers may flow out of the ‘local area’ through the ‘neighbourhood’ to the edge of a ‘city’. The endpoints of the different arrows provide an indication of the likely location and scale of discharge of unsafely managed excreta to the environment.

The SFD Graphic represents the excreta produced by the total population of an urban area from the point where it originates. It therefore includes excreta from households, schools, institutional toilets, hospitals, workplaces etc. The places where excreta originate are known as categories of origin in the SFD Manual (see Part A, section 2.2. 1 of the SFD Manual, Version 1.0, October 2015: Excreta flows may need to be split between different categories (for example home and school) and this must be clearly stated in the report.

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

The width of each arrow on the SFD Graphic is proportional to the percentage of the population whose excreta contribute to that flow, not volumes of excreta or waste. This is because data on the types of sanitation systems used is normally available via national census data or health surveys, and is based on the number of people. To convert this data to volumes would require a large number of assumptions to be made such as:

  • the amount of waste each person produces per day
  • the amount of water used to flush the waste in water-based systems
  • the amount of leakage in sewers etc.

Typically very little data is available to enable accurate or credible estimates to be made on the basis of volumes. Population percentages are also relatively easy to comprehend for non-technical stakeholders.

The SFD Graphic shows the percentage of the population whose excreta are considered to be either safely managed or unsafely managed. Safely managed and unsafely managed in this context indicates the likelihood of a population being exposed to a hazard as a result of the flow of excreta through the sanitation service chain, rather than absolute risk. Estimating the absolute risk would require accurate information on the level of hazard (concentrations and volumes of known pathogens at any point in the service chain), etiology and dose-response curves for those known pathogens, and information on the timing, duration and age profile of population exposed to the hazard; assessing these would require significant additional data collection and analysis.

The SFD Graphic and process is related to the sanitation service chain; the service chain for solid waste would be different. The SFD Graphic Generator cannot be used directly to model solid waste flows across a city or town, but the existing SFD Manual (Version 1.0, October 2015) and process could be adapted to develop solid waste flow diagram tools.

Other tools have been developed that also explore the flows of faecal waste through the sanitation service chain. These include:

  • The Faecal Waste Flow Calculator, developed by the IRC (, approximates shit flow volumes along the sanitation service chain. As mentioned in FAQ 5, numerous assumptions are required when converting the percentage of the population’s excreta to volumes and we recommend caution.
  • The Performance Assessment System (PAS) for urban water supply and sanitation developed by CEPT University ( This tool is based on a questionnaire which is filled in for a city or town to assess performance indicators on water, sanitation, and solid waste management. It then identifies key strengths and areas for improvement.

This process originated from the work of Andy Peal, Barbara Evans, and the World Bank on faecal sludge management which is documented in the following papers:

  • Fecal sludge management (FSM): analytical tools for assessing FSM in cities. By Andy Peal, Barbara Evans, Isabel Blackett, Peter Hawkins and Chris Heymans. Published September 2014, 4 (3) 371-383; DOI: 10.2166/washdev.2014.139.
  • Fecal sludge management: a comparative analysis of 12 cities. By Andy Peal, Barbara Evans, Isabel Blackett, Peter Hawkins and Chris Heymans. Published December 2014, 4  (4)  563-575;  DOI: 10.2166/washdev.2014.026.

The Process

A good way to start the SFD process is by reading the SFD Manual (Version 1.0, October 2015): (

This tells you what data you need to collect and how to collect it:  Part A - Annexes A and B of the Manual are particularly helpful. To have a common understanding of terms and use consistent language, it is important that you review part D of the SFD Manual, titled as Glossary. We also recommend that you read through previous SFD Reports, especially if one has been produced for a city or town in your country, as this will highlight data sources which you can use, and will give an idea of the layout and content of the report. All SFD reports are available via If you require help, remember that you can always contact us via the help desk or by email This email address is being protected from spambots. You need JavaScript enabled to view it.. A pool of experts, all of whom have developed SFD  Reports using this process, is happy to answer any questions and guide you through the process. 

The terms desk-based and field-based are used in the reports prepared in the Phase 1 of this project, following the methodology recommended in the SFD Manual (Version 1.0, October 2015). They are not related to where you undertake the study, but relate to the level of data collection and analysis required; a detailed explanation is available in Part A of the SFD Manual (Version 1.0, October 2015), (

The type of study you do will depend on three things:

  • the amount of time you have available
  • the accessibility of information
  • the resources you have

Higher levels of all three are required for a field-based study. A desk-based study can be seen as a preliminary study that can be built upon when more resources and data become available. It should be noted that the distinction regarding field vs desk-based studies is likely to be changed in the next version of the manual, based on the learnings of piloting the method in 40 cities worldwide.


Stakeholder engagement is a critical part of the SFD process. It is necessary as a means of gaining acceptance and support for the study. Experience has proven that higher the level of stakeholder engagement, more likely the SFD Report and SFD Graphic will be used by decision makers. Guidance on stakeholder engagement can be found in Part B the SFD Manual (Version 1.0, October 2015): (

The amount of time required to complete an SFD Report will depend on the level of study you develop, the amount of data available, and your access to key informants. In general a desk-based study takes less time than a field-based study. During the piloting of our methods we found that a desk-based study took between three to five weeks and a field-based study took up to two months. Where you are familiar with the town or city being studied, the time involved is likely to be significantly shorter. It was also found that significant additional time may need to be factored in for stakeholder approval of the final SFD Report.

A good starting point can be official documents from governments, such as census data or strategic plans. In addition, documents, studies and reports from institutions working in the town or city, e.g. NGOs or UN Agencies, can be very helpful sources of information. Municipalities, utilities or private local service providers may keep useful records relating to their activities such as design documents, legislation and bylaws, yearly reports, licenses, treatment plant registers, etc.

We also recommend that you read through previous SFD reports produced for a city or town in your country, as this may highlight data sources which you can also use. SFD reports are available via

There are likely to be gaps in the data for your town or city. You should try to fill these gaps by looking at grey literature (internal, unpublished reports) and conducting key informant interviews. Wherever possible, any data should be cross-checked (triangulated) with data from other sources. You will probably have to make assumptions about your city and town. When assumptions are made you should state clearly in the report the logic behind them. These assumptions should also be clearly explained in Section 7 of the Executive Summary (see SFD report Template available at By reviewing the reports from other cities you can see how other authors have overcome the lack of data.

The efficiency of the treatment plant is affected mainly by:

  • The operation and maintenance of the plant and
  • The burden of the amount of waste arriving at the treatment plant on the designed capacity of that plant

Data about this can be found from:

  • Municipality plans, design, and budget
  • Key informant interviews with the operators of the plant
  • Registers from the treatment plant (vacuum tanker arriving)
  • Observations
  • National standards and effluent measures

Based on this, the efficiency can be determined regarding the standard parameters and effluent quality; if the effluent does not meet the national standards the efficiency cannot be considered 100%. If the facility is well maintained and it is not working under capacity, the treatment could be considered to be at least partially treated (50%). If the effluent is not monitored then assumptions regarding operation and based on expert opinion can be made as long as the report shows all the assumptions made by the author. For instance, in Kumasi, where effluent is not being monitored, it was assumed that the plant was partially treating the waste due to the following observation: although there was a lack of maintenance and the amount of waste arriving was close to the treatment capacity limit (working some days over capacity), the treatment plant was still working and the effluent was of a nationally accepted quality.

Where possible, authors must agree on the percentage of waste being treated with the relevant stakeholders. In the absence of specific data the following three percentages can be used as a guiding principle: 0% where there is no treatment, 50% where there is “some” level of treatment, and 95% where almost all the waste is being treated.

The SFD is a good first step for a city or town that wants to address sanitation challenges. It represents a preliminary assessment which can help to identify important data gaps, priority areas for further analysis or to gain consensus on the need for critical interventions. The process of assembling the data for an SFD can facilitate better information sharing and a more accurate appraisal of the current situation from a wide range of stakeholders. The potential of the SFD process is being documented by the SFD Promotion Initiative; case studies can be found at SFD case studies.