Dual flush toilet

The system was developed by Japanese sanitary product manufacturer TOTO in 1960.{{cite web|url=https://www.toilet-kyoukai.jp/history4|title=【歴史】手洗付隅付ロータンク|publisher=Japan Toilet Association}} It was equipped with two levers and built-in hand-washer, and also notable in that it reused the water in the hand-washer for flushing. However, it was not very commercially successful either in Japan or internationally. In 1976, American industrial designer Victor Papanek proposed the dual flush system in his book Design for the real world,{{cite book|last1=Papanek|first1=Victor|title=Design for the real world:Human ecology and social change|date=January 1976|publisher=Chicago Review Press|isbn=978-0897331531|url=http://playpen.icomtek.csir.co.za/~acdc/education/Dr_Anvind_Gupa/Learners_Library_7_March_2007/Resources/books/designvictor.pdf|access-date=25 July 2014|quote=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' }} but the first practical implementation was designed in 1980, by staff at the Australian sanitary-ware company Caroma, with flush volumes of 11 and 5.5 litres.{{cite web|url=http://www.biotechnology-innovation.com.au/innovations/instruments/flush_technology.html|archive-url=https://web.archive.org/web/20070829045837/http://www.biotechnology-innovation.com.au/innovations/instruments/flush_technology.html|url-status=live|archive-date=2007-08-29|title=Dual Flush Technology|access-date=2019-01-04}} The design caught on, and a redesign in 1994 cut water usage to 6 and 3 litres.

The dual-flush toilet has become almost universally adopted in Australia, New Zealand, Singapore, Sweden, Israel and many other countries, with its use in new buildings often mandated by legislation in those countries.[http://www.powerhousemuseum.com/australia_innovates/?behaviour=view_article&Section_id=1040&article_id=10044 Household and clothing: Dual flush toilet], Powerhouse Museum. Accessed: 15 February 2015. The more complex dual-flush mechanism is more expensive than many other types of low-flush toilets.{{cite web|url=http://home.howstuffworks.com/dual-flush-toilet2.htm|title=How the Dual Flush Toilet Handles Waste|date=11 November 2008|publisher=How Stuff Works|pages=2|access-date=2009-07-08}}

;Push-button

Due to being a development of 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. The lack of siphoning also means that the toilet requires less water to operate. Due to this, the waterline is considerably lower than that in siphon-flush toilets.

The toilet has two buttons on the cistern rather than the single-flush one; one button delivers a lesser amount of water (eg. 3 litres) and the other a greater amount (eg. 6 litres).{{cite web|url=http://www.hgtv.com/decorating/the-lowdown-on-low-flow-toilets/index.html|title=The Lowdown on Low-Flow Toilets|publisher=HGTV|access-date=2009-07-08}} It also uses a larger 10 cm trapway in the bowl, allowing for water to come out faster and clear the bowl efficiently.

;Lever

There are also dual-flush toilets that use a siphon valve operated by a lever rather than buttons, with a ≤ 6L full flush, and a ≤ 3L half-flush if the flush handle is held down{{cite web |url=https://www.vivasanitary.co.uk/news/how-a-dual-flush-syphon-works.aspx |title=How a dual flush syphon works |newspaper=Https |date=8 September 2017 |author=Allan Hanson |access-date= 4 January 2019}} or released immediately after flushing.{{cite web |url=https://www.youtube.com/watch?v=juWZS-La_vo |archive-url=https://ghostarchive.org/varchive/youtube/20211220/juWZS-La_vo |archive-date=2021-12-20 |url-status=live|title=Macdee Motion dual flush syphon |website=YouTube |date=8 September 2017 | access-date= 25 October 2020}}{{cbignore}}

;Tipping bucket

The tipping bucket cistern can operate in a dual flush mode when the lever is rotated halfway 2.5/5 litre.{{cite web |url=https://www.waterflush.fr/en/ |title=Water Flushdual flush | date=8 September 2017 | access-date= 25 October 2020}}

The dual-flush toilet typically uses less water, resulting in lower running costs and less environmental impact. It was promoted by the Australian Government under its "Target 155" campaign.{{Cite web|url=http://www.ourwater.vic.gov.au/target155/saving-indoors|archive-url=https://web.archive.org/web/20090519015502/http://www.ourwater.vic.gov.au/target155/saving-indoors|url-status=dead|archive-date=2009-05-19|title=Our Water, Our Future|publisher=State Government of Victoria|access-date=2009-07-08}} The first dual-flush toilets had a 4.5 litre (half) and 9 litre (full) flush, but innovations by Caroma brought that down to 3 litres and 4.5 litres respectively, achieving a WELS rating of 4 and 5 stars in Australia.{{Citation needed|date=June 2016}}

Australian governments have used rebates to encourage the replacement of old single-flush toilets with more water-efficient ones.[http://www.toiletrebate.com.au Toilet Rebates] {{webarchive|url=https://web.archive.org/web/20100418000225/http://www.toiletrebate.com.au/ |date=April 18, 2010 }} 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,{{Cite web |url=http://www.ourwater.vic.gov.au/saving/home/rebates/products|archive-url=https://web.archive.org/web/20080721061525/http://www.ourwater.vic.gov.au/saving/home/rebates/products|url-status=dead|archive-date=2008-07-21|title=Our Water, Our Future - Eligible Products|publisher=State Government of Victoria|access-date=2009-07-08}} New South Wales, The ACT or South Australia.

In Britain, the cost of a dual-flush mechanism which can be retro-fitted to an existing toilet was estimated to be from about £15 in 2007.{{cite news |last1=Callard |first1=Sarah |title=Is it worth it? Installing dual flush |url=https://www.telegraph.co.uk/news/earth/3308766/Is-it-worth-it-Installing-dual-flush.html |access-date=2019-05-31 |work=Daily Telegraph (UK) |date=2007-09-29}}

While dual flush reduces running cost, the initial purchase price is higher, and replacing a toilet entails installation cost. In many cases, it is possible to replace the flushing mechanism of an existing installation; such retrofitting can cost about US$30.{{cite web|url=http://www.greendaily.com/2009/02/10/dual-flush-toilet-for-30/|archive-url=https://web.archive.org/web/20090211144807/http://www.greendaily.com/2009/02/10/dual-flush-toilet-for-30/|url-status=dead|archive-date=2009-02-11|title=Dual Flush Toilet for $30|access-date=2009-07-08}}

In the United States, the Energy Policy Act was signed into law in 1992 and took effect in 1994, requiring that toilets sold use no more than 6 litres (1.6 US gal) per flush. Fixtures that use a maximum of 20% less than the federally mandated maximum of 6 litres (1.6 US gal) receive the WaterSense label, a US Environmental Protection Agency (EPA) program designed to encourage water efficiency in the United States.{{Cite web |title=20 Years of the Energy Policy Act: 18 Trillion Gallons Saved Through More Efficient Toilets |url=https://www.allianceforwaterefficiency.org/news/20-years-energy-policy-act-18-trillion-gallons-saved-through-more-efficient-toilets |access-date=2023-12-25 |website=Alliance for Water Efficiency |language=en}}

For dual-flush toilets to receive this label, the average flushing volume of two reduced flushes and one full flush must be below 4.8 litres (1.28 US gal).{{Cite web|last=Environmental Protection Agency|date=June 2, 2014|title=WaterSense Specification for Tank-Type Toilets, Version 1.2|url=https://www.epa.gov/sites/default/files/2017-01/documents/ws-products-spec-toilets.pdf}}

While all dual-flush toilets are commonly seen as water-saving, this does not apply to all designs. In the US, some dual-flush toilets have flushes of {{Convert|1.6|and|1.28|USgal|l}}, which do not fulfill criteria for the WaterSense label and thus cannot be classified as high-efficiency toilets.{{Cite web |url=https://toiletvision.com/dual-flush-toilets/#not-water-saving |title=Dual flush toilet. Not water saving |access-date=11 January 2020 |archive-date=22 December 2019 |archive-url=https://web.archive.org/web/20191222130943/https://toiletvision.com/dual-flush-toilets/#not-water-saving |url-status=dead }} Based on the WaterSense averaging rule over two reduced flushes and one full flush, a dual-flush toilet with a full flush at the US legal maximum of {{Convert|1.6|USgal|l}} must have a reduced flush of {{Convert|1.12|USgal|l}} or less to meet the WaterSense standard of {{Convert|1.28|USgal|l}} on average. A common combination for dual-flush toilets meeting the WaterSense standard is a reduced flush of {{Convert|1.1|USgal|l}} and a full flush of {{Convert|1.6|USgal|l}}.{{Cite web|url=https://lookforwatersense.epa.gov/Product-Search-Results-Toilets.html|title=WaterSense Product Search - Toilets|website=lookforwatersense.epa.gov|accessdate=22 March 2023}}{{Cite web|last=Martin|first=Megabek|date=2021-11-23|title=Best Dual Flush Toilets With Maximum Water Savings In 2022|url=https://jumtimes.com/best-dual-flush-toilets-with-maximum-water-savings/|access-date=2022-02-22|language=en-US}}

Dual flush mechanisms are also more likely to develop leaks than a traditional siphon; the UK supplier Thames Water claimed in 2020 that dual flush toilets were likely to be wasting more water than they save due to a combination of leaks and confusion over which button to press.{{Cite news|last=Heap|first=Tom|date=2020-09-28|title=The water-saving device wasting billions of litres every week|language=en-GB|work=BBC News|url=https://www.bbc.com/news/uk-54326178|access-date=2022-02-22}}{{Not in citation|date=April 2024|reason=Two separate claims bundled into one, with sources being CEOs of companies with an obvious axe to grind.

1 - not a "combination of leaks and confusion"; Thames Water "a British private utility company responsible for the water supply and waste water treatment" made a claim about button confusion.

1a - Thames Water, claims about "so many [loos] that continuously flow all through the day, collectively that water loss is now exceeding the amount of water they should be saving nationally" are NOT FROM A RELIABLE NOR IMPARTIAL SOURCE.

Thames Water are NOTORIOUS for leaks, so much that they are being re-nationalized.

https://en.wikipedia.org/wiki/Thames_Water#Leakage

Also, while making claims of "400 million litres (88 million gallons) of water lost daily from loos" - Thames Water "Freedom of Information requests revealed that Thames Water leak levels were at their highest for five years. It was estimated to be losing 630 million litres (140 million imperial gallons) a day.[61]"

2 - regarding other leaks claims, those were from a manufacturer of siphon flushes; "Thomas Dudley Ltd, one of the UK's largest plumbing manufacturers" whose CEO wants "drop valves outlawed" - while the Bathroom Manufacturers Association "chief executive Tom Reynolds admits drop valves are more likely to leak" - BUT - "if not maintained", with the maintenance part being tucked into another part of the article, though being from the same source. That's not objective reporting, that's pushing an agenda.}}

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