Simplified Sewerage

This web site is aimed at giving support for the publication
PC-Based Simplified Sewerage Design
and it accompanying Windows based design program.

Links are also given to publications on this and other low cost sewerage systems

AND IN FRENCH (as of 19 Jan 2011) see the download page



PC-Based Simplified Sewerage Design was published by the School of Civil Engineering, University of Leeds, UK, in January 2001. It is a manual and windows based design program for use in the design of the simplified sewerage system. It was published with the aim of promoting the use of simplified sewerage throughout the developing world. To quote the preface of the manual:

"Simplified sewerage is an important sanitation option in peri-urban areas of developing countries, especially as it is often the only technically feasible solution in these high-density areas. It is a sanitation technology widely known in Latin America, but it is much less well known in Africa and Asia. It is the purpose of this Manual to disseminate this technology more widely in the developing world, so that it can be used in peri-urban sanitation programmes and project to improve the health of poor communities. However, simplified sewerage is not just for peri-urban areas - it can be successfully and appropriately used in middle-and upper-income areas as well.

We hope that this Manual serves its purpose of making simplified sewerage better known throughout the developing world, and that the PC-based design program contained herein facilitates the hydraulic design calculations."

How To Get The Manual and Program

The manual and program are both available to be downloaded from this site.

  1. The manual in .pdf format can be viewed or downloaded here and
  2. Details of how to download the design program can be found here.

If you require a copy of the manual and program on CD please send a request either via e-mail to Professor Duncan Mara <> or via post to this address:

Prof. D Mara
School of Civil Engineering
University of Leeds
Woodhouse Lane
Leeds LS2 9JT

Note that there is a limited supply of printed manuals and CDs.

Simplified Sewerage Description

Simplified sewerage is an off-site sanitation technology that removes all wastewater from the household environment. Conceptually it is the same as conventional sewerage, but with conscious efforts made to eliminate unnecessarily conservative design features and to match design standards to the local situation.

Various approaches to reduced-cost sewerage have been developed in different parts of the world, often independently of each other. The Manual, and accompanyingPC Based design program, draw on the approach developed in the early 1980s by the CAERN, the Water and Sewerage Company of the north-eastern Brazilian state of Rio Grande do Norte. The aim of CAERN was to develop a technically feasible and socio-culturally acceptable solution to the previously intractable problem of sanitation provision in high-density low-income peri-urban areas (de Andrade Neto, 1985; Guimarães, 1986; Mara 1996; de Melo, 1994; Sinnatamby, 1983 and 1986; Sinnatamby et al., 1986). The simplified sewerage approach is now widely used through Brazil.

Key features of the system are as follows:

(a) Layout: in order to reduce costs, CAERN developed simplified sewerage as an in-block system, rather than – as with conventional sewerage – an in-road system. The key feature of an in-block system is that sewers are routed in private land, through either back or front yards. This in-block or back-yard system of simplified sewerage is often termed condominial sewerage in recognition of the fact that tertiary sewers are located in private or semi-private space within the boundaries of the `condominium’.

(b) Depth and diameter: simplified sewers are laid at shallow depths, often with covers of 400 mm or less. The minimum allowable sewer diameter is 100 mm, rather than the 150 mm or more that is normally required for conventional sewerage. The relatively shallow depth allows small access chambers to be used rather than large expensive manholes.

Figure 1 Costs of conventional and simplified (condominial in-block) sewerage, and on-site sanitation in Natal in northeast Brazil in 1983. Source: Sinnatamby (1983).

Figure 2 In-pavement (sidewalk) simplified sewerage being installed in the high-income area of Lago Sul in Brasília in 1999.


In-block sewerage, particularly back-yard sewerage, can significantly reduce the length of sewer required, thus reducing costs. Costs are further reduced by laying sewers at shallow depths away from heavy traffic loads. The results are illustrated in Figure 1, which shows that, as the population density increases, simplified sewerage can become cheaper than on-site sanitation systems. In Natal, the state capital of Rio Grande do Norte, this occurred at the relatively low peri-urban population density of 160 persons per hectare.

In Natal, the capital costs of simplified sewerage in 1980 were US$ 325 per household, compared with around US$ 1,500 per household for conventional sewerage. CAERN was able to recover its costs over a 30-year period by surcharging the monthly water bill by only 40%, rather than the 100% that was the norm for conventional sewerage. The monthly charge for water was US$ 3.75, the `minimum tariff’, based on an assumed unmetered consumption of 15 m3 per household per month. Thus, the cost of simplified sewerage to the householder was only US$ 1.50 per month.

Similar levels of cost saving have been recorded elsewhere. In Orangi, Pakistan, the cost of community-based sewerage installed with technical assistance from the Orangi Pilot Project (OPP) was found to be about one quarter of that of conventional sewerage provided by government agencies (see Reed and Vines, 1992a, b and Zaidi, 2000). At around $40 per household, the absolute costs of these sewers was much lower than in northeast Brazil. This was partly because of much lower construction costs and partly because the sewers were built by the users themselves. Regardless of the absolute cost, the important point is that simplified sewerage offers substantial costs savings over conventional sewerage and is thus more likely to be affordable to the urban poor.

The fact that simplified sewerage is low-cost does not mean that it can only be used in low-income peri-urban areas. CAESB, the water and sewerage company of Brasília and the Federal District in Brazil, now regards simplified sewerage as its standard solution for sanitation in rich and poor areas alike (Luduvice et al., 1999; see also Nigreiros, 1998). This preference for simplified sewerage must be seen in the context that rich areas of Brasília are very rich indeed (Figure 2).

Simplified sewerage has been successfully used in countries other than Brazil. In Latin America, for example, it is used in Bolivia, Colombia, Nicuagua, Paraguay and Peru (Guimarães, 2000). In Africa it has been implemented in a few trials in South Africa (Pegram and Palmer, 1999), and in Asia it has been very successfully used since the mid-1980s by the National Housing Development Authority in Sri Lanka, with over 20 schemes now in operation (Ganepola, 2000); it has also been used in Karachi, Pakistan (Sinnatamby et al., 1986) and Malang, Indonesia (Foley et al., 2000). In India, however, and despite the technology being included in the national sewerage and sewage treatment design manual (Ministry of Urban Development, 1995), it has not been used, even though its applicability is very high, especially in "slum networking" sewerage projects (see Diacon, 1997; see also Chaplin, 1999).

Simplified Sewerage design program

The latest version (1.0) of the Simplified Sewerage design program can be downloaded by clicking on this link. Download Page

Instructions for installation and use

Download to a convenient directory, then execute the program.
This will bring up a small window asking if and where you want to unpack the program and the network data files.
Accept the default or choose a directory and click the start button.

After unpacking itself the Simplified Sewerage program will then install.

A program group named Simplified Sewerage will be created under the Start menu.
Click on the tap icon located here to start the program.

(For more details, including information about updates, see the notes on the Download Page)

Program Help
As from version 1.0 the install package includes a help file.
This has a full description of all screen and functionality of the program.

Example Files
In the Help files you will see a heading Quick Start Examples under this are described four examples.
Files for these examples may be found in the Networks folder where the program was installed.

E-mail Help
Should you require any further help or have any questions or useful comments
you may e-mail me here:

Last updated: 18 May 2001