How it began
Bruce Thompson led the design team at Caroma, a bathroom products maker in Adelaide, in developing a dual-flush toilet cistern in 1980. The project was backed by 130,000 dollars of government assistance. Caroma had grown out of a plastics business started by Charles Rothauser, a Hungarian-born designer who opened a factory in the Adelaide suburb of Norwood in 1941 and whose company had earlier made a one-piece plastic toilet cistern.
How it works
The cistern, sold as the Duoset, had two buttons and two flush volumes, 11 liters and 5.5 liters. The user chose the smaller flush for liquid waste and the full flush for solids. The toilet bowl also had to be redesigned so that the smaller volume of water could still clear the waste.
How it spread
In 1994 Caroma redesigned the toilet in porcelain with a cistern giving 6 and 3 liter flushes and a matching bowl, halving the water normally flushed away. That version drew attention in the European sanitaryware market, and exports began soon after. Australian water utilities describe the dual-flush toilet as a common feature of Australian bathrooms. The Caroma brand continues with products made overseas, but the company's Norwood premises closed in 2017.
What changed first
When the Duoset was trialled in a small South Australian town it saved 32,000 liters of water a year per household. Caroma's success led to laws in every Australian state except New South Wales making dual-volume toilets compulsory in new buildings. In 1982 the cistern was a finalist for the Prince Philip design prize.
