Urinary Diverting Toilet (UDT) part 1

A personal benefit from lockdown has been a slowing of pace, allowing a bit more time for contemplation and thinking , in particular at what we should be prioritising at the CradleArk. Part of this process also is the focus on trying to do something constructive with the materials at hand, rather than being able to rush off and buy what we think might be suitable for the project.

One of the many challenges still facing South Africa (And the Cradle Ark) is the lack of suitable toilet facilities.  This also affects the crèche “Encedweni  Education Centre” and is one of the requirements of registering a school. Parents also balk at the thought of the present bucket system and their children being exposed to it.

Traditionally because of lack of water , this has been approached by what is known in South Africa as the”long drop” or sometimes referred to as a “pit toilet” or “pit latrine”. Whilst this does address the immediate problem , it does result in further problems such as people falling into the toilet and our news sadly carries such stories on a regular basis. Multiple users also cause the toilet to fill up , with the associated smell , flies etc making the use of such facility rather unpleasant and even degrading.

Digging the pit requires a lot of effort and in some areas may be very difficult due to soil type and presence of rocks.

The average flush toilet uses between 8 -13 litres of water a flush so if you extrapolate this in a community  like CradleArk, even with the population just using the toilet once a day, say 150 people x 10 litres , the entire delivered water supply will be used within two days only on the toilet!

Thus even if more water was supplied the extravagance of such a system using precious water, is not ideal in a dry country. What then are the immediate alternatives?

  • There is the bucket system but apart from it’s many shortcomings , this has a negative connotation relating back to the apartheid era.
  • There is the septic tank system but this uses a flushing mechanism. Would this be feasible if there was a sufficient supply of water and the water could be re- used ? We will consider this option and combining the system with a worm set up to process the solids , remove pathogens and allow the water to irrigate crops. There could be some negative perception about this route, especially if the community wanted to on sell the crops so this would have to be carefully thought through.
  • There is the solar dehydrating method whereby hot air is pumped into the receptacle drying out faeces and these are later removed. The advantage of this system is that some of the pathogens are removed.
  • The UDT is a water efficient composting toilet, which uses a medium like wood-shavings to cover faeces and then these are mechanically removed. As we do not have available water at present we would like to investigate this method based on the following criteria and implement a trial run with a prototype to see if the technology could be rolled out, to help other communities. We would like to combine existing ideas and see what the end result is.

Wikipedia shows that the “eThekwini municipality” has introduced these UDT toilets, on a large scale but as yet are not using any of the composting benefits, so testing could benefit that project further.

The criteria for our toilet.

  • It must not smell and must be easy to keep clean
  • It must be reasonably simple to make and cheap out of readily available materials.
  • It should allow for future modification to incorporate “waste processing”
  • It must be water efficient.
  • The later prototypes must not only work but also look decent


As we plan to grow duckweed the separation of the urine is useful as this can be processed by the duckweed and be a food source for the duckweed resulting in a reusable water source.


Commercial units are available and if the project is a success then a moulded UDT might be the way to go in the long run. However, locally the units are “very expensive”  and installation of multiple units might be too costly. What then about making our own?


In researching and looking at the options the most interesting design is that by Dennis Donahue ( http://dennisdonohue.blogspot.com/2013/12/composting-toilets_15.html )and involves making the UDT from two modified buckets. This is appealing as the repurposing of HTH buckets immediately comes to mind and a steady supply of these is available. The buckets are also white plastic adding to the “porcelain” type look. What is also appealing is the scaling can be easily changed with small buckets more suitable for the nursery school. I also like the fact that we should be able to source different coloured buckets for the kids – maybe pink for the girls and blue for the boys. In addition to the UDT toilet the boys would have a separate urine catcher available functioning on the principle of a urinal.


Thus begins out thought process with building an initial simple prototype. Thereafter it needs to be tested and any design flaws revealed.


At this point there are various angles we would like to investigate that will develop through this process. The use of a solar de-hydrator  on the faeces,  a solar driven fan, a mechanized removal of the faeces such as an auger type setup, processing of the faces using worms or alternatively Black Soldier Fly (BSF). A completely different approach could also consider the UDt as the basis for generating methane gas (as a fuel source?)



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