City Spends Millions On Pipes

The recently approved mid-term adjustment budget provides for an amount of R54,2 million for upgrading of water networks. The City’s 11500 km pipe network comprises rigid materials such as cast iron and coated steel. In the more recent past, internally bitumen coated fibre cement pipes were used and these days the most common material for use in suburban streets is the more flexible UPVC pipes that are able to withstand small movements without fracturing or bursting.

The other main reason for bursts can be high internal water pressures, particularly at night, which physically burst the pipes at a weak point. Pipes in the City’s network are sized to be capable to overcome the friction of water in the pipes, so that even at the peak periods in the morning and again in the evening, there is sufficient water for everyone.

As water is normally gravity fed from the service reservoirs on the hills surrounding the city, the water pressure in the pipe network will rise substantially once the majority of people have stopped taking water, sometime to more than twice the daytime working pressure.

To overcome this, the City started a programme some years ago for the installation of major pressure reducing valves that work in whole suburbs to adjust the water pressure as it rises. The first of these, the largest in the world at the time, was installed almost 10 years ago in Khayelitsha and another major scheme was installed in Mitchells Plain in 2008.

Several other smaller scale pressure management projects are currently underway in Lwandle, Delft, Fisantekraal and Gugulethu. Commissioning of the Atlantis project will take place shortly. Pressure reduction devices will continue to be installed throughout the city, where these projects will show beneficial results. A start needed to be made and this has initially been focused in those areas where water losses have been the highest and where we can best put into practice our Water Conservation and Water Demand Management Strategy.

The majority of pipes requiring replacement are 100 mm diameter, and these are replaced at an average cost in excess of R1000/m. Approximately 6km was replaced in 2006 and this figure has grown to 46km being achieved in 2008/09 financial year. As mentioned before, some 21km of pipe has already been replaced in this financial year.

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