Dual flush toilet

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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 invented by Australian inventor Bruce Thompson in 1980 while working for Caroma,[1] and although the first generation dual-flush toilet caught on, a redesign in 1993 cut water usage in half when used properly.[1] Due to the more complex mechanism, it is more expensive than many other types of low-flow toilets.[2]


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.[2] 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-gallon (3 litre) and 1.6-gallon (6 litre) capacities.[3] 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.[3]

Instructions for how to use a dual-flush toilet in Currier House at Harvard University


The dual flush toilet system, due to its ability to save water, has been promoted by the Australian Government under its Target 155 campaign.[4] Dual flush toilet suites started out with a 9/4.5L flush, however, innovations from Caroma, Australia's leading bathroom brand, have brought that down to 4.5/3L flush, achieving a WELS rating of 4 and 5 stars in Australia.

Australian governments are encouraging the replacement of old single flush toilets with more water efficient toilets through toilet rebates.[5] 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,[6] New South Wales or South Australia. Sydney Water’s rebate program ended on 30th June 2011. [7]


Despite the high water-savings quality the toilet has a few disadvantages. It may be slightly more expensive than other low flow toilets.[2] Certain retrofitting systems have brought the price down significantly, costing approx. $30 USD.[8]

"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."[9]


  1. ^ a b "Dual Flush Technology". Retrieved 2009-07-08. 
  2. ^ a b c "How the Dual Flush Toilet Handles Waste". How Stuff Works. p. 2. Retrieved 2009-07-08. 
  3. ^ a b "The Lowdown on Low-Flow Toilets". HGTV. Retrieved 2009-07-08. 
  4. ^ Our Water, Our Future. State Government of Victoria. Retrieved 2009-07-08. 
  5. ^ Toilet Rebates
  6. ^ Our Water, Our Future - Eligible Products. State Government of Victoria. Retrieved 2009-07-08. 
  7. ^ Dual Flush Toilet Rebate. Sydney Water. Retrieved 2012-11-19. 
  8. ^ "Dual Flush Toilet for $30". Retrieved 2009-07-08. 
  9. ^ Elliott, Sara.  "How Dual Flush Toilets Work"  11 November 2008.  HowStuffWorks.com. <http://home.howstuffworks.com/dual-flush-toilet.htm>  06 August 2013.

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