The SFD Graphic is produced as a png (picture file), pdf (portable document format) or svg file (scalable vector graphic).  With experience, by simply adjusting the input data users can draw any scenario, and are expected to document this process in the accompanying report.  Alternatively, minor layout edits can be done in the svg file using graphic editor programmes, like Adobe Illustrator or Inkscape. Please contact the SFD Helpdesk in order to find out how to make appropriate adjustments.

In Step Two of the SFD Graphic Generator, users enter the proportion of the contents of each type of on-site container which are faecal sludge and which may be periodically emptied from tanks and pit latrines.  The remaining fraction is dealt with in different ways depending on the types of systems.  For guidance on what value to enter, users can refer to the detailed schematics of each system in the SFD Glossary. A general summary of recommended values is given below.  These values should be used in cases where there is no specific additional data on which more accurate estimates can be made:

Where tanks are connected to soak pits, use the default "100%" value. This will model the proportion of the contents which are emptied periodically (you will enter this value in the SFD matrix under F3) as 100% faecal sludge. The remaining not emptied fraction is made up of faecal sludge, which remains in the container, and infiltrate which soaks into the ground.  For systems in locations where risk of groundwater pollution is low, this fraction comprises variable F8. For systems in locations where risk of groundwater pollution is significant, this fraction comprises variable F15. (Refer to schematics L7 & S2)

Where tanks are connected to water bodies or to open ground use the default "100%" value. This will model the proportion of the contents that are emptied periodically (you will enter this value in the SFD matrix under F3) as 100% faecal sludge. The remaining not emptied fraction is made up of faecal sludge, which remains in the container and supernatant discharging to water bodies or open ground.  This fraction comprises variable F15. (Refer to schematic L9) 

Where fully lined tanks have no outlet or overflow, use the default "100%" value. This will model the contents as 100% faecal sludge and a proportion of this may be emptied periodically (you enter this value in the SFD matrix under F3). The remaining not emptied fraction is made up of faecal sludge and supernatant, which remain in the container. This fraction comprises variable F8. (Refer to schematic L10)

Where lined tanks with impermeable walls and open-bottoms and/or pits (all types) have no outlet or overflow (for example many “cubluks” in Indonesia), use the default "100%" value. This will model the contents as 100% faecal sludge and a proportion of this may be emptied periodically (you enter this value in the SFD matrix under F3). The remaining not emptied fraction is made up of faecal sludge, which remains in the container, and infiltrate which soaks into the ground. For systems in locations where risk of groundwater pollution is low this fraction comprises variable F8. For systems in locations where risk of groundwater pollution is significant this fraction comprises variable F15. (Refer to schematics L11 & S4)

Where septic tanks and fully lined tanks are connected to a sewer network, use a value of "50%". This will model half the contents as faecal sludge and a proportion of this may be emptied periodically (you enter this value in the SFD matrix under F3). The remaining not emptied fraction will comprise faecal sludge, which remains in the container, and is represented by variable F8. The other half of the contents is modelled as supernatant discharging into the sewer network, represented by variable S6. (Refer to schematic L6)

Where lined tanks with impermeable walls and open-bottoms are connected to a sewer network, use a value of "50%". This will model half the contents as faecal sludge and a proportion of this may be emptied periodically (you enter this value in the SFD matrix under F3). The remaining not emptied fraction will comprise faecal sludge, which remains in the container, and infiltrate which soaks into the ground. For systems in locations where risk of groundwater pollution is low this fraction comprises variable F8. For systems in locations where risk of groundwater pollution is significant this fraction comprises variable F15. The other half of the contents is modelled as supernatant discharging into the sewer network; where there is a low risk of groundwater pollution this is represented by variable S6, and where there is a significant risk of groundwater pollution this is represented by variable S7. (Refer to schematics L6 and S3)

Where tanks are connected to open drains, use a value of "50%". This will model half the contents as faecal sludge and a proportion of this may be emptied periodically (you enter this value in the SFD matrix under F3). The remaining not emptied fraction will comprise faecal sludge, which remains in the container and is represented by variable F15. The other half of the contents is modelled as supernatant discharging into the open drains, represented by variable S7. (Refer to schematic L8)

In situations where there is a mixture of sanitation system (for example, some septic tanks are connected to soak pits and some are connected to open drains) , the user can calculate the ratio of the systems to estimate the proportion of the content of the tanks which is faecal sludge.

If Open Defecation in your city equals 0%, then ticking this box and clicking “Draw SFD Graphic” will cause a gold star to appear next to the open defecation box on the SFD Graphic.

Each cell of the SFD Selection Grid represents a system. You can select each one by clicking on it, and deselect it by clicking on it again.

If you only want to deselect one system, click on it and it will disappear; then click the “Create SFD Matrix” button. This will redraw the matrix without that system, but ALL other data is kept.

If you want to keep working on the same city but start afresh, then deselect all the systems, select the new set of systems and then click “Create SFD Matrix”. This will draw a new SFD Matrix, which is empty and ready for you to populate with data but the general information data you entered about the city will be retained.

To clear all data and start a new SFD, click the reset button  located both at the top and bottom of the SFD Graphic Generator page. This will clear all input data - the city general information input boxes, the SFD Selection Grid and the SFD Matrix data - enabling you to start again. But before you do these, remember to save any data you want to keep.

The SFD Selection Grid in Step One of the SFD Graphic Generator allows the user to choose from a number of frequently used technologies for example; toilets connected to sewers, septic tanks and fully lined tanks, as well as those using different types of pit latrines.

The SFD Selection Grid can also be used to model other systems and some suggestions for how to do this are included follows below:

• Twin-pit latrines in areas where there is a low risk of groundwater pollution: in Step One, select “Lined pit with semi-permeable walls and open-bottom with no outlet or overflow”, this is system T1A5C10. In Step Two, on the SFD Matrix, input the proportion of the population using the system in the first box and then in the next available box to the right, under F3 “proportion of this type of system from which faecal sludge is emptied”, input 0%. Since the FS remains in the container until it is safe to handle, the SFD Generator models the excreta as “FS contained – not emptied”, i.e. safely managed and therefore a green arrow (F8) on the SFD Graphic. (F4 and F5 should also be set to 0% on the SFD Matrix).
• Twin-pit latrines in areas where there is a significant risk of groundwater pollution: in Step One, select “Lined pit with semi-permeable walls and open-bottom with no outlet or overflow”, this is system T2A5C10. In Step Two, on the SFD Matrix, input the proportion of the population using the system in the first box and then in the next available box to the right, under F3 “proportion of this type of system from which faecal sludge is emptied”, input 0%. Since there is a significant risk that the FS will cause pollution of groundwater used as a drinking water source, the SFD Generator models the excreta as “FS not contained – not emptied”, i.e. unsafely managed and therefore a red arrow (F15) on the SFD Graphic. (F4 and F5 should also be set to 0% on the SFD Matrix).
• Composting toilets and Dehydration vaults (used with urine diverting toilets): in Step One, select “Fully lined tanks (sealed) with no outlet or overflow”. This is system T1A3C10 and will model the excreta as “FS contained” on the graphic. In Step Two, on the SFD Matrix, input the proportion of the population using the system in the first box and then in the next available box to the right, under F3 “proportion of this type of system from which faecal sludge is emptied”, input 0%. Since the FS remains in the container until it is safe to handle, the SFD Generator models the excreta as “FS contained – not emptied”, i.e. safely managed and therefore a green arrow (F8) on the SFD Graphic. (F4 and F5 should also be set to 0% on the SFD Matrix). In the case of urine diverting dry toilets, the urine fraction is also considered to be safely managed and included in the green arrow F8.
• Container-based toilets: in Step One, select “Fully lined tanks (sealed) with no outlet or overflow”. This is system T1A3C10 and will model the excreta as “FS contained” on the graphic. In Step Two, input the proportion of the population using container-based toilets in the first box and then in the next available box, under F3 “proportion of this type of system from which faecal sludge is emptied”, input 100%. This indicates that all users have their container emptied regularly. Next, under F4 “proportion of faecal sludge emptied, which is delivered to treatment plants”, enter the proportion you estimate is delivered to treatment. If the service is functioning well, this is likely to tend to 100%. Finally, under F5 “proportion delivered to treatment, which is treated”, enter the proportion you estimate is treated. This proportion is considered safely managed and will be represented by a green arrow labelled “FS treated” (F5) on the SFD Graphic.
• Aqua-privy toilets: in Step One, select “Septic tanks” and the relevant technology that it is connected to from List B. For instance, if it is connected to a “soak pit” and there is a low risk of groundwater pollution, select T1A2C5. This will model the excreta as “FS contained” on the graphic. In Step Two, input the proportion of the population using aqua-privy toilets in the first box and then in the next available box to the right, under F3 “proportion of this type of system from which faecal sludge is emptied”, input the proportion of the aqua-privy toilets from which faecal sludge is emptied. Next, under F4 “proportion of faecal sludge emptied, which is delivered to treatment plants”, enter the proportion you estimate is delivered to treatment. Finally, under F5 “proportion delivered to treatment, which is treated”, enter the proportion you estimate is treated. This proportion is considered safely managed and will be represented by a green arrow labelled “FS treated” (F5) on the SFD Graphic.
• Hanging latrines: in Step One, select “No onsite container connected to a water body”. This is system T1A1C7 and will model the excreta as “FS NOT contained” on the graphic. In Step Two, input the proportion of the population using hanging latrines in the first box.

When modelling these systems, remember to state clearly in the SFD Report the method used, any assumptions made and any concerns identified relating to the actual management of the systems.

If there are multiple systems and the SFD Graphic is complex, this is likely to be a 1% rounding error, which is unavoidable with so many calculations. If it is larger than this, then it is more likely to be an error in the input data and users are advised to check their working. Where a small rounding error is encountered which makes understanding difficult and/or delays agreement amongst stakeholders, then users are encouraged to make minor adjustments in the estimated percentages to eliminate this.  If this proves difficult you can contact the SFD Helpdesk who will endeavour to identify the problem and provide assistance with making the most appropriate adjustments.

In many cities the definitions of septic tanks, lined tanks and various types of pit are used interchangeably. It is therefore important that those providing the data for the city understand the types of sanitation system in use and how they function. When producing an SFD it is recommended that where possible discussions are held with stakeholders to ensure that the functionality of each system is understood. You can use the Sanitation System Classification Tool to help select from the SFD selection grid the correct sanitation systems in use in your city. If you require any assistance in classifying the system you are considering the SFD Helpdesk would be happy to help you.

There are many terms used to describe the locations that a containment technology can be connected to, so it is not possible to include them all on the SFD selection grid; therefore generic terms have been used for the options in List B along the top of the grid. In making the right selection, it is important to consider how the system functions, rather than just what it is called locally. For example, in some cities toilets discharge to covered drains, which are not shown on the SFD selection grid as an option. When producing an SFD it is recommended that where possible discussions are held with stakeholders to ensure that the functionality of each system is understood. You can use the Sanitation System Classification Tool to help select from the SFD selection grid the correct sanitation systems in use in your city. If you require any assistance in classifying the system you are considering the SFD Helpdesk would be happy to help you.

In some locations it is common for toilets, pits or tanks to be connected to storm drains which are covered and referred to locally as sewers. However, since the covering is often done informally with the covering being incomplete and/or not extending over the full length of the drain, they do not separate humans from excreta. Where used, this practice can therefore present a significant public health risk and for the purposes of the SFD, the excreta is considered NOT contained. Therefore when using the SFD Selection Grid, any toilet, pit or tank technology connected to an open drain, storm drain, storm sewer, or open sewer (covered or otherwise) should be classified as being connected "to open drain or storm sewer".

The efficiency of the treatment plant is affected mainly by:

• The operation and maintenance of the plant
• 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 risk of groundwater pollution can be estimated using the groundwater pollution risk estimation tool in the SFD Graphic Generator on the SFD web portal.  Risk in this case is a function of both the probability of pathogens from sanitation systems reaching groundwater and the probability of exposure to this hazard by people drinking that groundwater. The user is prompted to answer six questions in order to obtain an estimate of the risk of groundwater pollution.  Risk can be estimated for the city as a whole, or separately for different areas of the city. The tool provides a general estimate expressed as either ‘low’ or ‘significant’ risk, which can then be used to select appropriately from the SFD Selection Grid.

To assess risk of groundwater pollution you will need information on the:

• Vulnerability of the aquifer
• Lateral separation between sanitation systems and groundwater sources
• Percentage of drinking water produced from groundwater sources
• Water production technology used to extract groundwater

Remember to state clearly in the SFD Report the data used and any assumptions made.

The SFD Graphic shows the percentage of the population whose excreta is either safely managed or unsafely managed. Generally, data on sanitation services at the household level are expressed in terms of the percentage of population, but further along the sanitation chain data are more commonly expressed as volumes per day; for instance wastewater flows and faecal sludge deliveries to a treatment plant. Local expert opinion and the views of local stakeholders can help in agreeing a method for converting these volumetric flows to population-based estimates. The factors that may need to be considered include:

• Volume of excreta produced per person per day
• Volume of water used per day for flushing water-based systems
• Accumulation rate of faecal sludge in tanks and pits per day
• Exfiltration/leaching rate of pits per day
• Volume of leakage per day from sewers etc.

Remember to state clearly in the SFD Report the method used and any assumptions made.

For each type of onsite system the user needs to enter a value for the variable F3 “proportion of this type of system from which faecal sludge is emptied”.  The true value is a function of the percentage ever emptied and the proportion of the contents removed during emptying.  However, estimating both these may be challenging.   

The SFD Process defines emptying as “the manual or motorised emptying of faecal sludge from onsite sanitation systems”. The emptying event or service should remove a substantial amount of the faecal sludge from the container which would then be transported away and should certainly comprise more than just unblocking septic tanks or flushing out pit latrines. However, the SFD Process does not define an acceptable emptying frequency; this is very context specific and dependent on many factors. 

A pragmatic approach is to estimate the proportion of households with a specific type of system who ever have them emptied.  In some cases there will be data from household surveys and situational analyses. There may also be data on the capacity of the emptying service providers (i.e. numbers and volume of trucks) and their service history; these could provide a useful cross-check.  In many locations however these data will not be available.  Calculating F3 will then depend on expert opinion and should be discussed by stakeholders as part of the SFD process.  It is important to state clearly in the SFD Report the method used and any assumptions made.

These terms are clearly defined in the SFD Glossary.  There is no difference in the way that the SFD process models the performance of decentralised and centralised sewers.  This distinction is included to facilitate discussion in cites/towns where there is both a centralised sewer network and one or more small scale or pilot decentralised systems which may have distinct performance characteristics.  In that case, different percentages can be assigned to variables, for example the percentage delivered to treatment and percentage treated in each case.

In some locations pit contents are "flooded out" or "flushed out" when full: that is, the side of the pit is broken open to allow the contents to flow out, or the contents of the system are flushed out using water. This often occurs during the rainy season. These systems should be categorised as "Toilet failed, damaged, collapsed or flooded" connected to "Open ground".

In other situations people use "pit diversion": that is, another hole is dug next to the pit in use and the contents are then drained, flushed, or otherwise transferred into the new hole. For the purposes of the SFD, if the contents of the hole are backfilled and covered over so that humans are separated from excreta, the contents are considered "contained". These systems should be classified as "Toilet never emptied but abandoned when full, adequately covered with soil". However, if the contents are NOT properly covered over with a significant risk of humans being exposed to the excreta, then the contents are considered "NOT contained" and these systems should be classified as "Toilet never emptied but abandoned when full, NOT adequately covered with soil".