Usability for Human Beings: the Shower Tap

Usability is a hot topic in Software Development these days and, while it's mostly common sense and applies everywhere, people still treat it as arcane lore. In this (occasional) series, I will focus on real life examples of (mostly bad) usability to try and demystify the matter and show how a little bit of thought can go a long way.


I was recently confronted with the following shower mixer tap

  

It is actually an ok looking chrome object, with a tap on the right that allows you to set the temperature while twisting the tap on the left controls water flow and commutes between the top and the handheld shower heads.

But, can you spot what's wrong?

The problem with it is that, while the reflections in the photo may fool you to think otherwise, both taps are absolutely smooth: there are no grooves or dents to increase friction and help you turn the taps.

While it was no problem operating it with dry (and wet) hands, when my hands were full of soap and shampoo it become impossible (literally!) to turn the tap without first rinsing my hands. Only, of course, I could not rinse them because I had temporarily turned the water off. At a guess, I would say an elderly person with arthritis won't be able to use this tap at all!

This became immediately apparent to me the first time I used it, and it beggars belief that a company the size of Roca let that pass!

Interestingly enough, the right tap while also smooth, has a small dimple to allow you to lock the set temperature and keep you from unwittingly turning it and scalding yourself (a good usability feature). Not only that, this very same bump helps you turn it with soapy hands if you do decide to use it!

Suggested improvement: Though it may not be as aesthetically pleasing, they should add some texture to the tap surface. Making the tap turning a lot looser could help, but experience tells me taps tend to harden with age so this is not a good substitute in the long run.