Waste water from millions of lavatories, showers and baths in drought-stricken Cape Town will be treated and pumped into the massive Cape Flats aquifer - and will be used again for drinking water.
As the drought continues to bite deep, Capetonians have become used to reusing water in their homes, but drinking water that may have flushed your neighbour's loo will take water saving to another level.
The City council says using waste water, which includes treated sewage effluent, to recharge the aquifer is "part of the plan".
Ironically, the treated waste water will help clean the aquifer water, which has become so contaminated by urban pollutants that in some parts, it is not drinkable.
According to a study by Umvoto Africa, one of the City's main partners in developing models for abstraction from the Cape Flats aquifer, the treated waste water will dilute the underground water that has been contaminated by run-off from informal settlements, industrial sites, wastewater treatment plants, dumps, pesticides, fertilisers and cemeteries.
The aquifer is big, stretching more than 400 square kilometres from Milnerton and Tygerberg Hills in the north, across the Cape Flats to the False Bay coast, as far as Gordon's Bay.
But with experimental drilling into the aquifer already under way, farmers in the Philippi Agricultural Area (PHA), who have been drawing on water from the Cape Flats aquifer for years, are worried that the City's proposed abstraction from the aquifer - up to 80 million litres a day - could threaten their water source and livelihoods.
The PHA Campaign, made up of some of the farmers supported by more than 60 NGOs and individuals, have now called on the City and provincial authorities to provide legal protection for the area, which they say is the primary recharge area for the aquifer.
Spokesperson Nazeer Sonday said they agreed with using the aquifer water, but it needed to be done in a managed way with a recharge plan.
"This drought is an unprecedented crisis. We will be the first city to run out of water. We need to put systems in place to prevent us getting in this situation again," Sonday said.
One option was that instead of pumping millions of waste water into the sea, the City should clean it and put it in the aquifer to replace what was taken out.
Asked to comment, councillor Xanthea Limberg, Mayoral Committee Member for informal settlements, water, waste services and energy, said this was part of its plan.
"That is what the City's groundwater model is based on," she said.
Limberg said they were working with geohydrology experts to create a model so the aquifer could be used both for abstracting water and a place to store water, like a natural underground dam.
"The city is looking at ways in which alternative water sources can be used for aquifer recharge," she said, treated waste water being one.
The Department of Water and Sanitation would assess the information the City provided before granting a licence to use the aquifer water.
Capetonians used 531 megalitres (Ml) of water a day last week. The City's target is 450Ml million a day.
Dams are an average of 23.6% full.
When they reach 13.5% - Day Zero - the day taps will be turned off and citizens will have to collect water from tankers - will kick in.
Day Zero is currently set for July 15.