Some building projects have had to rely on expensive imported water with others postponed indefinitely because of shortages -- in a region where one in ten jobs are in construction.
The Rabie Group, a large construction company, uses treated effluent water to make concrete and wash equipment on its Cape Town sites.
"Obviously these factors all have a price tag which will invariably push up construction prices," warned Rabie director Miguel Rodrigues.
In 2016, 94 percent of the region's companies flagged water as a risk to their operations.
Companies have not yet faced a blanket limit, but instead struck agreements with officials -- often at huge costs.
"You want to avoid creating the crisis within the crisis... the construction industry is already very fragile, cutting off their water risks creating job losses," councillor J.P. Smith, who is responsible for safety in the city, said.
The city council is even working with behavioural scientists and the University of Cape Town to determine the best way to "nudge" businesses and residents to slash consumption.
Cape Town's success in cutting domestic consumption -- by 60 percent in three years -- is expected to be highlighted during World Water Day on March 22.
Christopher Smith, a senior engineering assistant at the Koeberg nuclear power station outside Cape Town, said that the plant has developed its own desalination system in response to the drought.
"I don't see any option, we just have to bite the bullet," said Smith, 60, as he stood in line for water at the Newland Spring collection point beside the SAB Miller brewery.
The beer giant, owned by AB InBev, declined to comment on the drought's effect on beer production, but others in the drinks industry told AFP that if "Day Zero" happened, it would be catastrophic.
"If we run out of water, the whole industry will be mucked up," said Raphael Clistini, 28, a South African-born entrepreneur who travels the world opening temporary bars.
His most recent venture was the Gin Dock, a pop-up bar that overlooked the city's famed Victoria and Alfred Waterfront and the iconic Table Mountain.
Clistini serves gin distilled in the city -- but the water may soon have to be brought in from Johannesburg, 1,400 kilometres away.
"It's going to raise the price. Everything is going to cost more," he said.