At a recent Artesia brainstorming session, the subject for discussion was demand reduction.
Talk turned to forecast versus realised benefits of demand reduction, and the often simplistic assumptions made in forecasting water efficiency savings.
Take the case of one of the largest consumers of water in the domestic environment, the toilet cistern.
It’s true that most of the mighty cast iron Victorian siphons, with their thunderous roar that sent terrified children running for the door have long gone, and modern plastic replacements have a much lower flush volume- or rather two flush volumes. And that’s where the behaviour bit comes in.
“Why”, a certain person scoffed; “people don’t even know which button to press”.
A soul with more humility then piped up; “Er… which button do you press?”
“The big one, obviously, its an easier target”, “no, the small one- it indicates lower volume”, “I just do a short or long press of both”.
In this group of water saving experts, it turns out that there was no consensus on a generalised rule of how to operate a dual flush toilet – after all, who keeps a toilet instruction manual. And if we don’t know, what is the chance that the majority of the population know – or care.
Design needs to be more intuitive, or even a little awkward to obtain the full flush – such as an operation that means performing two actions rather than one. The savings could be considerable. Let’s make an estimate using some conservative figures (this also allows for workplace urinals).
Assumptions:
- Half of people in the UK press both buttons simultaneously or the wrong button as a routine.
- A half flush reduces volume from 6 to 4 litres.
- Every person uses a toilet six times a day, of which 4 should be half flush.
- Potential volume saved per person per day= 8 litres
- Number of people using flush inefficiently= 30 million
- Potential saving = 8 litres * 30 million per day = 240 megalitres a day, or roughly 10% of UK water network leakage.
While water companies invest in education and communication programmes on this topic, there is an inherent design barrier.
How could this be brought about? Designs that use nudges (two handed operation for full flush being more of a shove), such as a more obvious placement of half flush on top of cistern, and full flush on the side, or even making the half flush a more pleasing operation- there could be some form of ‘reward’ such as a pleasing or satisfying noise. This might particularly appeal to children.
Alternatively, the full flush actuator could be made off-putting- an enjoyable idea to explore, but perhaps not for the market.
Either way, some kind of conformity between designs would help; they can vary considerably for no good reason. This is the type of thing that would need to be addressed by a standards commission, and that is where my particular interest in the subject ends.
