Johannesburg Water says a fire that broke out at City Power's Brixton substation on Sunday has affected their water systems.

"It's still unclear at this stage what the cause of the fire and the extent of the damage is," it said in a statement on Sunday night.

"As a result of the fire, pumping from Johannesburg Water's Brixton reservoir to the Brixton tower will be affected." 

City Power spokesperson Isaac Mangena said the substation along Fulham and Ripley roads in Brixton had caught fire around 18:00.

"According to the preliminary investigations, it was triggered by overloading. Unfortunately, by the time the fire department arrived on site, the damage was already extensive and nothing could be salvaged," he said.

"Every piece of equipment was reduced to ashes. City Power is now in the process of appointing a contractor to conduct an overall assessment today and give an estimation of the financial losses and the duration required to complete the repairs."

City Power said every piece of equipment was reduced to ashes.

Mangena said the Hursthill Service Delivery Centre (SDC) was in the process of ordering two mini-substations, a Ring Main Unit (RMU), cables and joints.

"Additional material may be required after the assessment. We are ramping up efforts to try and shorten the the duration of the outage to customers in Brixton, Rossmore and surroundings," he added.

This affected the water supply to the Brixton reservoir and tower zones. Joburg Water said a pumping unit would be arranged for the Helen Joseph Hospital.

Over the weekend, Johannesburg Water warned customers that water towers and reservoirs in the City would take some time to fully stabilise following a disruption at the Eikenhof pump station due to a power failure. 

However, Mabe said there was "significant recovery" due to Rand Water's systems "causing a positive knock-on effect" on Johannesburg water infrastructure.