Cape Town looks to pressure management to ensure efficient use of water
Water supply to the City of Cape Town has been a challenge for many years, but new developments and new pressure management techniques are saving the city millions.

Before any new water transfer scheme is approved by government, a commitment is secured from the receiving Metro that certain demand management measures will be put in place to ensure the additional water will be used effectively and efficiently. 

The City of Cape Town has a long and impressive track record with the implementation of various water demand management measures, particularly the re-use of sewage effluent for irrigation purposes and pressure management.  This involves further treating the final sewage effluent to a quality suitable to be used safely to irrigate playing fields and golf courses, and in some cases, also for domestic irrigation of gardens as well as for certain industrial processes, with one consumer using roughly eight megalitres per day.

Pressure management
Pressure management is complicated and often misunderstood since it involves reducing the pressure of water supplied during off-peak periods. Pressure reduction should not be seen as a reduction in the level of service to the consumer, but rather an improvement.  

In recent years, there has been a growing awareness of the problems associated with excessively high water pressure being supplied to the public, and great advances have been made in the field of pressure management.  Various electronic devices are now available which allow the water manager to reduce excessively high water pressures during off-peak periods when consumers are not using significant quantities of water.  High water pressure not only damages household plumbing appliances but also causes high leakage from the system.  Such a problem is especially evident at night-time when consumers are asleep and very few are using water.  Most leakage and new pipe bursts occur at night between the hours of 8pm and 6 am.  Reducing the water pressure during this period will in turn reduce the leakage, reduce the occurrence of new burst pipes and help to prolong the life of the household plumbing systems. 

Cape Town the first
Cape Town was the first major city in the world to implement a large scale pressure management project specifically to reduce leakage during off-peak periods.  The large installation in Khayelitsha was the first and largest of its type in the world, when it was completed in 2001. This installation reduced the water wastage in Khayelitsha by approximately 1 000 cubic metres per hour, which represents enough water to fill an Olympic sized swimming pool every two hours. The installation has been fully operational for over six years and continues to save the City of Cape Town nine-million cubic metres per annum, or an amount of approximately R30-million.

Plans for Mitchells Plain
Several small projects have already been implemented and another large installation was recently approved to help control water pressures in Mitchells Plain. This is another large area which is relatively flat and low-lying and experiences excessively high water pressures during off-peak periods. The proposed installation will be similar to the Khayelitsha installation and will be one of the largest of its type in the world. The installation is expected to cost approximately R6-million and the savings are expected to provide a pay-back of less than a year. This installation will also help to prolong the life of the water reticulation system as well as protect the household plumbing fittings in every property. Further benefits from the proposed installation will be reduced sewage flow from the area and a reduction in burst pipes which in turn will provide a more reliable water supply to all residents.

Further details can be obtained from project manager Donnavin Wright or Melvin Engelbrecht:
Tel: +27 21 590 1417 or 1516, respectively
Email: donnavin.wright@capetown.gov.za