Small-bore sewers are sewage systems that use small diameter pipes, which are widely used around the world. However, many small-bore sewer systems face difficulties with technical issues like low gradients and leaks, financial issues such as underestimating operating costs, and management issues including lack of operator skills and monitoring. The study found that the feasibility of small-bore sewers is restrictive due to costs and dependence on other public services, and that building the infrastructure is not the main challenge - successful management is critical. Professional management is preferred over community-based organizations, and support is needed for the first years of operation.

1. SMALL-BORE SEWERS
Main learnings on a study made
in Africa, Asia and Latin America
Cécile Denormandie, AFD
Denis Désille, pS-Eau
Jean-Marie Ily, pS-Eau
Christophe Le Jallé, pS-Eau

2. Aims of our study
• Identifying strengths and
weaknesses, regarding
technical, financial and
management issues
• When small-bore sewers
are relevant?
• Which recommandations
for implementation?
© WSP

3. What are small-bore sewers?
© Reed

4. Small-bore sewers are widely
disseminated all over the world

5. But most of them face difficulties
• Technical issues: gradients are too low,
wastewater leakage, poor-quality concrete, etc.
• Financial issues: recurring operating costs are
under-estimated, too few connexions , low
collection rate of the sanitation fee , etc.
• Management issues: O&M skills are missing,
operator is not clearly identified
• Institutional issues: no contract, no monitoring,
no control

6. Main Learnings

7. Main learning #1
Feasability is very restrictive
• Money is needed (SBS is more expensive than
onsite sanitation)
• Other public services must be very efficient
(solid wastes, rainwater, access to drinking
water, land property…)
• A location for the treatment plant is
fundamental (except if the SBS is connected to
a conventional sewer)
• Users demand for SBS has to be confirmed

8. Main learning #2
Building SBS is NOT the main issue
There used to be mistakes in design and
implementation :
- slope is the main mistake !
- Pipes level higher than household
sanitation facilities level
- Waterproofness
- Etc.
BUT the main issue is management…

9. Main learning #3
Small sewer does not mean small management
• Sewer operator skills required:
– Responsive technical management
(4 levels of O&M)
– Financial management capacities
(tariff, invoices, balance of the
service, etc.)
– Marketing skills (to rise up number
of connexions)
– Social abilities (SBS is very sensitive
to bad users practices)
• A monitoring system, with control
and sanctions

10. © EAWAG-SANDEC

11. Conclusions
• Is SBS a proper solution to provide
sustainable sanitation services in pro-poor
contexts?
• Prefer management delegated to
professional authorities / companies instead
of CBOs
• Attention and resources should be dedicated
to support the post-project period (1 to 3 first
years of service management)

12. Coming soon, guidebook
« When choosing
and how to implement
and manage small-bore sewers »
© Hydroconseil
Thank You!