Toilet UX: a hot button issue

A toilet with push buttons of two different sizes, in a tiled room

Have you ever heard of UX, or user experience? Considering how, why and when users interact with a product or service has become big business, particularly in an age where we have detailed data to analyse it. Should you want to face utter frustration, give User Inyerface a try – a website devoted to demonstrating some of the worst practice in digital UX.

But not all UX experiences are that high-tech. Something as mundane as the humble toilet is still subject to the design process, with particular constraints and the need to balance function and form. Arguably the toilet needs to do this particularly well as it should never be language dependent. Since everyone excretes but not everyone speaks the local language, the need for a clear, simple and iconic user interface is crucial. Furthermore, the sheer volume of people who use toilets, and the essential need for a flush to work in order to wipe the slate clean for the next user (like a moist version of an Etch-A-Sketch) suggests toilet design can have a large impact on human society. Everyone should be able to speak toilet button.

One important facet of the toilet button interface is based around size. The concept of size is something we are all familiar with and tend to understand inherently – and as such is a key part of all design. Generally speaking, something that looks visually tiny indicates that in some way it is of a small magnitude compared with something larger. For instance, looking at a concept shot of the solar system – even if not drawn to scale (and they rarely are), you can determine that the Sun is larger than Jupiter, which in turn is larger than the other planets… and so on. Therefore it is quite logical to presume that, as far as design goes, something small is likely to have a smaller consequence than something larger. However, with the advent of ‘press-and flush’ toilet buttons, this design concept has run into some interpretation issues.

Once it was fully understood how terrible an impact humans are having on the environment, there was a marvellous little addition to our friend the toilet: a button, often but not always round, indicating a small flush and a large flush, a onesie or a twosie. This feature has become standard on a large number of toilets across the world… but, intriguingly, it does not always function in the same way.

Question: Is the small button the little flush (smaller amount of water) or the big flush (larger amount of water)?

It’s actually quite an interesting question, because it’s not as simple as it seems – and does vary.

There are two schools of thought in this issue:

Size: Since the small button is the smallest, it should produce the smallest effect.
Effect: Since we don’t want people to use the largest effect needlessly, we should make the button small so it’s harder to press/less obvious (this is almost like a toilet reverse psychology trick).

Another important factor here is what happens after, or as part of, an ‘error’ – if users often end up pressing both buttons in any case, there is an obvious design flaw. This is an issue about which many words have already been written; for example:

‘I have a two-button toilet. The buttons are two parts of a circle and are nearly the same size. I have no idea what they mean, so I always press both at once.’¹

‘It appears from visual inspection that the small button provides a smaller flush than the big one (these things are difficult to measure, but that seems sensible). But what happens if you press both, which is the easiest thing for my chunky fingers? Are they additive in some way, producing a megaflush? Or is that the same as the big button alone?’²

‘With a toilet you flush it. If a user cannot easily flush the toilet in a public restroom, that toilet design has indisputably failed. And with that failure comes wasted time, user embarrassment, sanitation issues, and unhappy customers.’³

These issues are not trivial: there are around 1.4 billion flush toilets in the world⁴, and most people use a toilet approximately 6-8 times a day⁵. Experts have suggested that users of flushable toilets are each ‘dumping up to 22 liters of drinkable water every day’⁶; they contend that just using flushable toilets is itself a global issue of great concern, never mind misusing them.

As we begin to design the user experience for interacting with the Cambridge Maths Framework, we have much to learn from broader design issues like this, in particular ones that are related to representing magnitude, size, comparative relationships and relative effect size. How can we make the user journey as intentional as possible by using well-established design research to guide and support Framework use without constraining it too much?

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