Dual flush toilet
A dual-flush toilet is a variation of the flush toilet that uses two buttons or handles to flush different levels of water. It was proposed by American industrial designer Victor Papanek in his 1976 book Design for the real world, but the first practical implementation was designed by Australian inventor Bruce Thompson in 1980, while working for Caroma. Although the first generation dual-flush toilet caught on, a redesign in 1993 cut water usage in half when used properly. The dual-flush toilet has since become almost universally adopted in Australia, New Zealand, Singapore, and Israel, with its use in new buildings often mandated by legislation in those countries. However, due to the more complex mechanism, it is more expensive than many other types of low-flush toilets.
The traditional Australian flush toilet, the dual-flush toilet differs from siphon-flush toilets in that it relies on gravity to remove waste from the toilet. In addition to its dual flush feature, the lack of siphoning also results in it requiring less water to operate. The lack of siphoning also means that it is similar to an aeroplane toilet; the water line is considerably lower than that of siphon-flush toilets. The main feature of the toilet is that it has two buttons for releasing water. It outputs water in both 0.8 US gallon (3 litre) and 1.6 US gallon (6 litre) capacities. The smaller level is designed for liquid waste, and the larger is designed for solid waste. It also uses a larger 4-inch (10 cm) trapway in the bowl, allowing for water to come out faster and clear the bowl efficiently.
The dual flush toilet, due to its ability to save water, has been promoted by the Australian Government under its Target 155 campaign. Dual flush toilets started out with a 9/4.5 L (full/half) flush, however, innovations from Caroma, Australia's leading bathroom brand, have brought that down to 4.5/3 L flush, achieving a WELS rating of 4 and 5 stars in Australia.
Australian governments have been encouraging the replacement of old single flush toilets with more water efficient toilets through toilet rebates. For dual flush toilets, with a star rating of 4 or higher, owners may be able to qualify to claim a rebate from the State Government in Victoria, New South Wales, or South Australia. Sydney Water’s rebate program ended on 30 June 2011.
As with most design changes, improvements are often a tradeoff with other factors. In this case, while the toilet achieves its goal of saving water, it may cost somewhat more than a single-flush toilet. (One should though factor in the cost of the saved water and not focus strictly on the purchase and installation costs.) If retrofitting an existing toilet, there is the additional cost of the building modifications; however  certain retrofitting systems have brought the price down significantly, costing approx. $30 USD.
The low water level in a dual-flush toilet may be slightly off-putting to visitors to Australia from countries where toilets with a full tank and one lever/button are the norm. A recent review stated:
- "Dual flush units are a little more expensive than other low flow toilet designs. There is also the problem of aesthetics. If you like a tidy toilet bowl that's half full of sparkling clear water, the dual flush concept will be a bit of an adjustment. Typically, dual flush toilets only retain a little water in the bowl, and flushing won't always get rid of all the waste. Even in full flush mode, there's some occasional streaking. With a dual flush toilet, you'll probably use your toilet brush more often, but then you probably won't need to keep the plunger nearby."
The above-stated negative with the low water level design would not occur to a native Australian, as all Australian flushing toilets, whether dual flush or not, have a low water level and reliance on gravity to complete the flush action.
- Papanek, Victor (January 1976). Design for the real world:Human ecology and social change (PDF). Chicago Review Press. ISBN 978-0897331531. Retrieved 25 July 2014.
Because what one does while sitting on a toilet differs in both quantity and quality, it seemed simple to redesign the apparatus so that one could select whether a great deal or only a minimal amount of water was needed for flushing. This concept again was rejected by my client - a man who makes his living manufacturing toilet bowls - as being 'in bad taste'
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- Household and clothing: Dual flush toilet, Powerhouse Museum. Accessed: 15 February 2015.
- "How the Dual Flush Toilet Handles Waste". How Stuff Works. p. 2. Retrieved 2009-07-08.
- "The Lowdown on Low-Flow Toilets". HGTV. Retrieved 2009-07-08.
- "Our Water, Our Future". State Government of Victoria. Retrieved 2009-07-08.
- Toilet Rebates
- "Our Water, Our Future - Eligible Products". State Government of Victoria. Retrieved 2009-07-08.
- "Dual Flush Toilet Rebate". Sydney Water. Retrieved 2012-11-19.
- "Dual Flush Toilet for $30". Retrieved 2009-07-08.
- Elliott, Sara. "How Dual Flush Toilets Work" 11 November 2008. HowStuffWorks.com. <http://home.howstuffworks.com/dual-flush-toilet.htm> 06 August 2013.