Australians have been harvesting rainwater, using low flow water fixtures and dual flush toilets for years.  In fact, dual flush toilets were developed by Caroma, an Australian company in the 1990s. You may or may not have seen a dual flush toilet before, but they are becoming more common in public venues such as sports arenas, shopping mall washrooms, and office towers.  One side of  the flusher will have a symbol of one water droplet, meaning flushes using 3 litres of water, while the other side will have 2 droplets, meaning it uses 4.8 litres to flush; ie: 1 means #1, and 2 means #2. Pretty easy! As Caroma points out on its website, toilet use in residences accounts for the most significant portion of residential water use, and an average family of four could cuts its water use by up to 72% just by installing and using dual flush toilets (and using them properly of course).

One of the best features of Caroma’s toilet, however, seems to be the fabulously generous drainage hole — known as a trapway in toilet speak. Unlike North American low flow toilets, where the trapway  is typically 2 1/8″ in diameter, the Caroma dual flush toilet’s trapway is 4″. What does that mean exactly? Well, when I was at Greenbuild in October, the Caroma people were demonstrating what their toilet could do, and they were flushing whole oranges without any problem whatsoever. Caroma uses a different flush technology than the North American standard, which has given Caroma dual flush toilets the reputation for rarely clogging. Caroma explains their technology best on their website:

North American toilets most commonly utilize siphon jet technology. Most of the water in the tank is used to create a vacuum or siphon effect in the trapway of the toilet bowl, which then pulls the waste out after the water. In the past, several North American toilets have been subject to clogging due to the lower volumes of water used in ultra low flow toilets. The trapways of the bowls had to be reduced to allow the vacuum to be created.

Washdown toilets do not use this flushing mechanism. When flushed, the water is released very quickly from the tank and into the bowl through an open rim bowl design. The water very effectively and efficiently pushes the waste out of the bowl, which is then followed by the water. The flush is fast and allows for superior movement down the sewage drains, as the water is following the waste. Because washdown toilets do not rely on creating a siphon effect in the trapway, the size of the trapway does not have to be reduced. Caroma toilets feature a massive 4 inch trapway, virtually eliminating the possibility of clogging!

[source: see “What is a Washdown Toilet?“]

Caroma’s website is full of handy information about their toilets. If you want to see a visual demonstration of Caroma’s technology, they’ve created an animated video of how it works:

Caroma invisi series II cube

Design: One of the latest trends in toilets is the “invisible tank,” where the tank is hidden behind the wall. While this practice is common in commercial settings, it hasn’t been available to residential use due to building design. However, in recent years, strides have been made in design and invisible tank toilets are the latest thing. If you’re like me and you’re hesitant about how you’d access the tank in the event that anything back there broke, the flush mechanism is accessible through the dual flush toilet plate, and the tank itself is guaranteed to be leak proof. Installing the tank and toilet separately also gives you the advantage of adjusting the height of the toilet, or even moving the flush plate to an adjacent wall.

Two one-piece designs were recently launched on the North American market as well. One piece toilet and tank designs make cleaning easier.

Finally, the last toilet is the Somerton Smart 270, a two piece dual flush toilet and a fully skirted bowl.

One final note about low flow toilets, the California Urban Water Conservation Council in partnership with the Canadian Waste Water Association, has tested hundreds of low flow toilets for their maximum performance levels (MaP levels). In other words, how much stuff you can flush down the toilet, and Caroma has listed the results for each model right on its website.

BEC Green

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