The Dual Flush Toilet 22 Sep 2005

39 comments Latest by Edward Heath

This is one of those posts I’ve been meaning to write somewhere for a long time, so here goes. I’m not sure how popular they are world wide, but in Australia, the dual-flush toilet is compulsory in all new bathrooms. We’re in an eternal drought, so using 67% less water is a good thing.

Don’t ask me how it happened, but somewhere along the way, I became fascinated (or at least mildly interested) with the various designs of the flush mechanisms. Yes, I’m about to use the word usable in the same sentence as toilet.

Whilst there are some perfectly usable “don’t make me think” designs out there (Caroma’s variations on their original design being a fine example), I have no idea what the designers/engineers of most models were thinking.

My personal favourite is the “push for full flush, pull for half flush” model in our house. Since my natural response (especially half asleep in the middle of the night) is to push a button, the toilet encourages me to do the wrong thing — it’s easier to waste water than it is to conserve it.

Others have a round button divided into two sections (about 1/3rd for the half flush), or some other equally complex (but “attractive”) design that makes it harder to do the right thing.

Perhaps it’s because I’m designing and building interfaces every day (and probably think about it all a little too much), but for every well designed website, tool, appliance or gadget I use, I feel like there’s hundreds or thousands more that seem to utterly ignore the basics of human interaction.

It’s no wonder my Dad still has a fear of programming the VCR, or that my girlfriend slams her laptop shut almost every night and announces that she “hates the internet”.

39 comments so far (Jump to latest)

Ian 23 Sep 05

OK, let’s see a Web 2.0 flush control. Are we talking icons or color keys?

martin hietkamp 23 Sep 05

oops … the url to “Caroma�s variations on their original design” doesn’t seem to work

Brett 23 Sep 05

I think that the toilet should know if i’ve done 1’s or 2’s and flush accordingly.

Or there should be a foot operated flush! :)

Anonymous Coward 23 Sep 05

I love the dual flush except when I accidentally press button 1 when number 2 is appropriate…

I long for three seashells….

Marten Veldthuis 23 Sep 05

Well think of it the other way, you don’t want to need a full flush but accidentally do just a half-flush.

Glen Murphy 23 Sep 05

I wrote an article on this once upon a time for some vaguely humourous publication, and my main point of contention was with the 1/3rd + 2/3rds flush buttons - there’s usually no labelling, so coming at it from a UI perspective it’s like “ok, is the big button for half-flush, and it’s big because you use it way more often than full flush? or is it big to indicate big water?”

I think I can credit a lot of my interest in UI design to the lengthy mock outrage I experienced at the design of these buttons.

Justin French 23 Sep 05

Link fixed.

Sam 23 Sep 05

Heh. My brother used to be obsessed by toilets and their mechanisms.

I’m intrigued that you find the circular button with unequal halves a bad piece of interface design. Dual-flush bogs are pretty common across Europe, and the split-button design seems utterly intuitive - press the smaller segment for a half-flush and the bigger segment to wash away that u-bend blocker.

I remember in my grandparent’s old house, in the exceptionally cold downstairs loo (out the back behind the kitchen with its freezing floor tiles, where I used to tiptoe as a kid to have a wee in the night so as not to wake the slumbering house) there was some abysmal flush device that required either a half-press or a full press. Neither action was easily accomplished, and you had very little idea whether you had successfully performed one flush or the other.

Even as a small boy, I can recall being quite surprised at how badly designed this was, and I wonder if, like Glen above, I can attribute my career in UI to that single, black and ice-cold cistern.

Donna Maurer 23 Sep 05

My daughter redesigned this when she was about 5. Her idea - pictures.

OK, the funny thing here is that we didn’t talk full-flush, half-flush. We talked about what was going to be flushed. I can’t quite get the courage to write it, so you will have to imagine what she thought would be good images.

Sergei Muller 23 Sep 05

At my previous job, we had the 1/3 half flush 2/3 full flush version.

The thing that made it easier to save water was that the full flush button was a bit heavier to press than the half flush button.

And… the half flush button was concave, so it had a nice little groove that your finger just naturally slipped into it.

dusoft 23 Sep 05


don’t be shy and tell us ;-))))) (I know, I know)

David 23 Sep 05

The dual flush toilet was one thing I was very impressed with when I went to Australia in 1993. I have wondered how long until they become common in the US, but there are very few models that are sold here and they often cost much more than the standard single flush models. One good sign was that Consumer Reports included them in their August 2005 review of toilets.

brian 23 Sep 05

Well, Justin, when you come to the US we’ve made it easy, it’s all handles, no buttons and _very_ rarely will you see a pull-chain. And in our ever obsession with being willing to waste water along with everything else, we only have one option - big flush.

A few years ago a buddy of mine told me “hey there should be toilets with big flush and little flush”. I thought, “yeah right, like that will ever take off”. Then I went to europe and saw them. What a visionary my friend was, and he had never been outside of the US! They were mostly the push button kind. I didn’t need any diagrams. Big button meant more to flush. I love the idea. I think we’re idiots here in the U.S. not to do it.

Rich 23 Sep 05

Doesn’t everyone know the difference between going number “1” and number “2”? Label the buttons “1” and “2”. Problem solved.

David 23 Sep 05

I know this is very common in the middle east, especially Israel. As far back as 15 years these types of toilets have been installed in new homes. When I purchase a new house, these toilets will definitely be going in them (NYC area).

dru 23 Sep 05

They have them in China too. I thought it was the coolest thing.

Dan Boland 23 Sep 05

That is pretty cool. It’s a lot better than the alternative, which is flush every other time you pee.

Darrel 23 Sep 05

If it’s yellow, let it mellow. Brown? Flush it down.

Mobil'Homme 23 Sep 05

I’ve used the Caroma recently and could not for the life of me fathom why it needed two buttons, nevermind which one to use. Having recently stayed in a hotel that had a toilet with a built-in bidet, I was frankly afraid lest I push the wrong button and release an unwanted jet of water from the Caroma (okay, in hindsight, that was an irrational fear given the location of the buttons atop the tank). In the end, I used both buttons. Probably not want the designers had in mind, but if you don’t know what the buttons are supposed to do it’s hard to assess whether they’ve done it.

Rob Cameron 23 Sep 05

First of all, let me just say that I’ve been obsessed with toilets since I was a kid. I even made a model one out of foam-core in 6th grade with a tape recorder that played the sound of the flush!

Here’s my solution to the half-flush/full-flush dilemma. Have a single button. When you do a normal press you get a half-flush. If you hold the button in, say for 2 seconds, you get a full-flush. This assumes that the person using said toilet knows it’s a dual-flush model. If not, and there’s something there that really needs some extra power, they ain’t gonna get it no matter how many times they press the button.

gotwood 23 Sep 05

darrel, my roommate has a penchant for putting that phrase into action. drives me insane - he eats a lot of asparagus, and you KNOW what that means. i say just pee in the sink and run the taps for a sec when you are done.

Greg Benedict 23 Sep 05

Why not use icons on the buttons that show something like a tank 1/2 full and a tank 3/4 with a down arrow in the bottom half of each tank?

GoClick 23 Sep 05

I’ve always longed for a standard of foot operated flushing in public rest rooms.

Don Wilson 23 Sep 05

Eternal drought? Where is the water going? :)

Todd W 23 Sep 05

The hotel I stayed at in Rome a couple of years ago had this feature, but in a more intuitive model (IMHO). There were two push buttons that together formed an oval shape kind of like ( ). The one of the left was smaller and almost looked like it was getting swallowed by the side on the right. So, the size difference made it clear that “use the smaller one for small flush, bigger for big flush.”

I found it brilliant and classically simple Italian design.

Anonymous Coward 23 Sep 05

How about an auto-sensing toilet that makes sure your brown always goes down with the min. amount of water?

Robert Wetzlmayr 23 Sep 05

Isn’t 2al flush standarT anyway? I haven’t met differing bowls for ages.

Thomas 24 Sep 05

Dual flush buttons have bugged for a very long time, actually… Some toilets like the one shown here and If� use meaningful signs. Other toilets have two different size of buttons, which is confusing: Does the big button give (1) a big flush becuase big=big or (2) a small flush because big button draws most attention and is easiest to push?
Surely one of life’s big questions.

Somebaudy 26 Sep 05

the #1 and #2 terminology does not exist in non-english languages. I’m french-speaking so I can’t report on ther cultures and languages.

jw 27 Sep 05

This reminds me of a great usability enhancement I read about… there were articles about these urinals (in holland airports?) that had a realistic-looking little fly painted on them.

human nature results in most men aiming for the little fly, which was placed where it would result in less splashing.

just a small and simple thing, taking advantage of a subtle bit of human nature to make something work better…. great, eh?

jeff 28 Sep 05

I like the hatbox toilet

Dave 02 Oct 05

I saw these in New Zealand first but they’re now becoming more and more commonplace in Ireland. The big difference I find between US and Irish/British toilets is the amount of water.

In the US the water is almost up to the rim in the UK/Ireland it’s about 5cms deep and only down at the bottom!

Joseph Comparetti 04 Oct 05

How about a flapper valve that converts a single flush toilet to a dual flush toilet. One push of the handle makes a half flush but one push followed by a tap of the handle makes a full flush.

Edward Heath 13 Aug 06

Hello; I have invented, patented (in many countries), and manufacture a product that is a simple toilet tank handle retrofit (remove and replace). For a liquidwaste flush, simply push the handle down until a swirl developes in the bowl (usually 2-3 seconds). For a full flush, push the attractive uniquely styled handle in 1/4” then down in the normal fashion. Effeciency and effectiveness is based upon the toilet bowl’s design and how well it is vented. A family of four will save approximately 18,000 gallons of clean water thus another 18,000 gallons of dirty water per year. Please e-mail me for more information if you like. Thank you