The Brixton 1 reservoir was critically low on Sunday.
Johannesburg Water (JW) said it closed the outlet on Friday, to manage available water, while replacing a valve.
Supply was re-routed to Hursthill 1, 2 and the Brixton 2 complex.
A power outage affected the Grand Central Tower and Pump station, making it impossible to pump water.
Pumping was expected to kickstart, upon the restoration of electricity supply.
A burst water pipeline that is 600mm long, hampered supply to Bryanston and Morningside reservoirs.
The Yeoville reservoir was also declining to critically low levels on Sunday, with pumping temporarily suspended to critically low levels.
Picture: Supplied