The Australians are credited with leading the way in the development of dual flush technology. In 1980, Bruce Thompson of Caroma Industries created the first two-button flushing system, a convenient method of manually selecting the water volume of each flush -- a half flush for liquid waste and a full flush for solid waste -- with the push of a button [source: Biotechnology Innovations]. Necessity was the driving force for the change. Traditional toilets used lots of water, a commodity that was in short supply on a continent that has erratic rainfall and experiences frequent and prolonged droughts.
The idea of evaluating waste to determine the most water-friendly way to getting rid of it caught on, and by 1993, a redesign reduced by half the amount of water used per flush. This led to international interest in the design. Most modern dual flush toilets use less than a gallon of water (3 liters, approximately) to flush liquid waste and around 1.6 gallons (6 liters) to flush solid waste [source: Nash]. This is a big savings over old toilet styles that used five gallons (19 liters) or more for each and every flush.
Today, dual flush toilets are used widely in Australia, Europe and Asia, and they're catching on in other areas as well. Increased environmental awareness, government regulation, the availability of monetary incentives and the rising cost of water are making the changeover to dual flush and low flow toilet designs more attractive to U.S. consumers.
So how do they work? In the next section, we'll take a look at how dual flush toilets handle waste.