In conventional water distribution, pipes are sized to enable peak instantaneous water requirements to be delivered at the regulation pressure. As these requirements are instantaneous, this means that much of the potential capacity is not used for most of the time. The system also has large flow variations depending on the demand at any instant.
By contrast, a trickle feed distribution system is sized to deliver the total daily volume at a continuous flow rate. This means a massive reduction in pipe diameters, and significantly less wear and tear on the system. In order for this to work, storage is required at all delivery points.Considering 95% of African water projects fail, a new approach is required.
Trickle feed systems involve lower capital expenditure which means that water can be brought closer to the home for the same money.
Systems involve smaller simpler and more maintainable technology
Systems can work on a prepaid basis, avoiding all the complexity of retrospective billing.
Water can be cheaply delivered to the household, so avoiding secondary contamination in buckets at home.
As the water usage is restricted, and paid in advance, people are encouraged to use their quota, this is unique in distribution systems, and encourages the increased water consumption required to reduce water washed disease.
Glover Development Engineers were involved in piloting two rural water projects using such a system. John Tipping (MSc Loughborough) ran the project as part of his research programme. His masters thesis is attached bvelow, and was dedicated to my late wife Stephanie… God bless him.
I strongly believe that trickle feed distribution is a major and important appropriate technology for sustainable water supply both in rural and urban situations. If you have been involved in piloting or implementing trickle feed systems, please send details so that I can provide contacts here. ([email protected])
Areas for Further Research
Sewerage requirements under trickle feed distribution- In view of the restriction of flow to each household, it should be possible to accommodate all waste flows in soakaways used in conjunction with onsite sanitation. Work is required to investigate the sustainability and restrictions of such a system, as well as the detailed technical/social/and ergonomic design of such systems.
Every technology has a social interface. Work is required into the sustainability of this interface for trickle feed systems. The maintenance, the tariff collection etc.
The systems we piloted involved the use of an orifice to restrict maximum flows. This may reduce the reliability of the system. In view of the reduced pipe sizes used throughout the distribution, the orifice may not be a vital component, and the tricklefeed system may function better (although less fairly and accurately) without. It would be valuable to investigate this.
In many development situations, engineers are expected to do all the major design work. Often engineers are not very experienced at hydraulics, and are in short supply, and are very expensive. I believe it is possible to develop straight forward rules for implementing a trickle feed system, which could be followed by technicians. This would massively increase the potential scope of water supply programmes. This is much more likely to work with trickle feed systems, where flows per household are set. Local technicians would then have rules to follow to extend existing schemes without requiring external engineer input.
Other bodies involved in trickle feed research include:
The Mvula Trust – South Africa
The Department of Water Affairs – South Africa
Durban Metro – South Africa
Partners in Development- Pietermaritzburg South Africa.