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Water throttling has its problems: Experts explain

An expert has warned that while City of Johannesburg’s water throttling may work to reduce demand‚ the method has its disadvantages.

The City of Johannesburg announced this week that it will start introducing water throttling in areas which have high consumption. This action follows the city’s experience that residents did not reduce their water consumption despite the city introducing penalties for not conserving water. The city needed residents’ help in reducing water usage by 15%‚ due to the drought.

Joburg Water said the throttling system will allow the city to reduce pressure in areas that use too much of the resource.

Professor Mike Muller of Wits School of Governance explained the process.

“When water supply is limited‚ it can be helpful to reduce the pressure in the main pipes. Water will then come out of taps more slowly. If there are leaking pipes‚ pressure reduction also slows down water loss‚” he said.

But Muller says there also problems with water throttling.

“There are problems in a hilly town like Johannesburg because if pressure is reduced too much‚ users in high lying areas may not receive any water. Supply may also fail to flats on the top of small blocks that do not have pumps‚” he said.

“The best outcome would be for all Johannesburgers to use water responsibly and to make conscious efforts to reduce their use. Citizens must also help Joburg Water by reporting leaks as soon as they are noticed. And Joburg Water must ensure that these are speedily repaired.”

In August‚ the Department of Water and Sanitation issued a government gazette compelling municipalities to reduce consumption by 15%. The cities of Tshwane‚ Johannesburg and Ekurhuleni have already introduced water restrictions and penalties to those who use the resource irresponsibly. However‚ none of the three metros have been able to achieve the required reduction in water consumption.

Marco van Dijk‚ chairperson of the South African Institution of Civil Engineering’s (SAICE) Water Engineering division‚ said people in the low lying areas could continue drawing water from the pipeline to a point that it gets dry.

“When the pipeline is empty‚ inside it’s a big problem. What happens now‚ if you have water on the outside of the pipeline due to a leak or sewer line that is leaking or ground water‚ dirty water is going to get into your water pipe. Your seals that join the pipeline work well if you have pressure on the inside because it closes nice and tight. If you have an empty pipeline and there is water on the outside‚ the seal does not work well and it allows water on the outside to get into the pipeline.

 “You can get contaminated water into the drinking water pipeline‚” Van Dijk said.

He added that one other issue putting the cities under pressure is the water that is unaccounted for. This is water stolen by people in the system and water that is lost through leaks.

 If the city has to reduce demand by 15%‚ it requires more assistance from the paying customers for it to meet the target as it must compensate for water that is not billed in the system‚ Van Dijk said.

 

 

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