Utility company Johannesburg Water is currently dealing with the largest repair of a burst pipe in the entity's history, the City said on Wednesday.
There were major leaks identified on the main water pipeline that runs through the Linbro Park landfill site, MMC for environmental and infrastructure services Nico de Jager said in a statement.
Affected areas include Sandton, Bryanston, Woodmead, Morningside, Alexandra, Linbro Park and the surrounding areas.
"This is the largest repair job ever done by Joburg Water on a main line," said De Jager.
He said the burst pipe was about 35 m deep, on a very unstable landfill, and they could not "risk burying our employees alive during the maintenance process".
De Jager said the burst pipe had affected water supply and had to be "throttled" to avoid reservoirs from running dry.
They hoped to flush the system around 12:00 on Wednesday and open the reservoirs, he said.
"Reservoirs shut down with 1 m of water left, so that they will have time to refill.
"High-lying areas such as Bryanston will take longer to receive water due to the height in relation to pumping capacity."
Estimated time of repair completion was 13:00, provided there were no further complications.