Gauteng is consuming more than 5 000 megalitres of water a day.

The unsustainable demand is why bulk supplier Rand Water has had to tighten the taps for the last ten days.

The spokesperson for Rand Water, Makenosi Maroo, said consumption remained the leading cause of Stage 2 water restrictions.

The heatwave, however, has not helped.

"Leakage or wastage of water has added to the high consumption. Dam levels are not the issue, the dams are almost full. We even increased the capacity of water supplied to Gauteng, but this has not helped," Maroo said. 

A week ago, Rand Water throttled its supply by 30% to get its reservoirs back up to the stable levels of 60%, from 38%.

Johannesburg Water purchases water from Rand Water and then reticulates it to homes and businesses within the city.

Nationally, 38% of the country's potable water is lost through leaks - but it is believed that, in Johannesburg, the statistic is more like 40%.

On Wednesday, Johannesburg's MMC for Environment and Infrastructure Services, Mpho Sesedinyane, met with Joburg Water officials to understand the cause of the water outages.

His focus was the Commando System - the towers and reservoirs that supply Hursthill, Brixton, and Crosby.

It feeds wards 58, 69, 86, and 87, which have experienced water supply issues.

According to Sesedinyane, the interruptions to the bulk water supply were caused by load shedding "or normal power failure on the Rand Water purification and pumping systems, as well as the Johannesburg Water pumping systems".

He said Joburg Water presented Sesedinyane with an analysis of the Commando System, as well as measures for the next two to four years at the reservoirs to ensure "sustainability of the water supply".

Sesedinyane has not elaborated on these measures.

His department, though, said all systems were now stable.

Johannesburg Water reported on Wednesday that the Brixton and Crosby reservoirs were recovering, while the Hursthill reservoir was low.

Meanwhile, on Wednesday, doctors at Helen Joseph Hospital in Auckland Park, and Rahima Moosa Mother and Child Hospital in Coronationville complained that there were still water issues.

Both were given extra supply from Johannesburg Water, and both have boreholes, but there was not enough water to supply all the facilities at the hospitals.