A power failure at a pump station feeding reservoirs and water towers caused taps to run dry in parts of Johannesburg and Pretoria, provincial utility Rand Water said this week.
This further aggravated residents who for months have had to plan mundane activities such as cooking and do laundry based on a daily blackout schedule.
Water and sanitation ministry spokeswoman, Wisane Mavasa said the government was working with water utilities "to improve the situation".
"(The) energy crisis is impacting the water infrastructure," she said.
One problem is that machinery is constantly being restarted because of power cuts, and this accelerates breakdowns, the government said.
Pump stations and water-treatment, which need a steady flow of power to work properly, have been badly impacted, it said.
Africa's most industrialised economy has been crippled by record power cuts in the past year, as troubles at debt-laden state energy firm Eskom worsened.
The utility provides about 90 percent of the country's electricity. And it's that electricity that runs water pumps.
Criminality has also contributed to the crisis, with Johannesburg's municipality saying hundreds of water tanks were stolen or vandalised in 2022.
Thomas Mabasa, a rail worker, said he had taken to showering at work -- a luxury not afforded to his children.
"(They) have to go to school without bathing," the 43-year-old told AFP.
He was among frustrated locals who took to the streets in Soshanguve, a township north of the capital, this week to protest the situation.
Demonstrators disrupted traffic, blocking roads with stones and waste.
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South Africans Fume Over No Lights, Water
"Sometimes we wait to see if the water will come back in the middle of the night to wake the kids up so they can shower before it runs out again," Mabasa said, as tyres burned on the street behind him.
Hospitals and schools have not been spared.
Kalafong hospital in Pretoria, endured two days of no water at the weekend.
Journalism student Ethel Malatji, 21, said her and colleagues at the Tshwane University of Technology in Pretoria were unable to cook, clean or bathe.
The problems have especially hit Johannesburg's Gauteng province, but not exclusively.
Cape Town has had to close some of its beaches due to a sewage spill following electrical faults at some of its sewer stations.
Increasing demand has also put a strain on supply in the country's southeast forcing authorities to implement water rationing.
That might become more common if energy and infrastructure problems are not addressed, said Dewald van Niekerk, who heads the African Centre for Disaster Studies at North-West University.
South Africa -- an already water-scarce country -- is set to experience extreme drought conditions in the next few years with the expected return of the El Nino warm weather pattern, he warned.