Types of toilet and their suitability
Practical Action
Simplified Sewerage
In response to the conventional conservative design criteria and in an attempt to reduce cost,
simplified sewerage has been developed. This results in less excavation due to pipes being
buried shallower and downstream pipes being shallower (as a result of reduced gradients) thus
reducing pumping costs. In addition material costs are reduced through smaller pipe diameters
and inspection chambers replacing manholes in some instances. The consequence of all these
improvements is to reduce the cost passed on to the final user (although comparatively this
could still remain high).
In some cases high population density, narrow streets, high groundwater and rocky ground can
make on-site sanitation problematic, in these cases simplified sewerage may be worth
investigating further.
Condominial Sewerage
The condominial approach to sanitation services (which can also be applied to water services)
was first developed in Brazil during the 1980s (Melo, 2005). In this system a service provider
will provide a sewerage connection point at the edge of a group of houses. The members of this
community are then expected to work together (possibly through CBO structures) to create
condominial sewerage that connects to this main sewer. The condominial sewerage generally
utilises simplified sewerage design criteria. A number of very successful programmes, such as
the Orangi Pilot Project in Pakistan, have used a similar technology.
Figure 1: Condominial Sewer Layout in Petrolina, Brazil
(Source: WELL, 1998)
Settled Sewerage Systems
These systems contain an intermediary tank on the house connection sewer. This system allows
the solids to settle out from the sewage and make the further transportation simpler. This lack of
solids means the sewer does not have to be laid on a constant gradient and can travel up and
down reducing the necessity for pumping and keeping sewer depths at a reasonable depth. The
systems were first developed in Australia as a means of conveying overflow from failing septic
tanks – a function that can be served in developing cities where septic tank effluent is not safely
absorbed into the ground.
2