As New Zealand heads towards what could be a drier-than-usual summer, here's an unusual way we might save water - stop flushing the toilet quite so often. 
 
The old water-saving advice goes: “If it’s yellow, let it mellow.” 
 
The problem is that many of us find an unflushed toilet really unpleasant. 
 
Now researchers at the University of Surrey have investigated a surprisingly simple solution - a pellet that dissolves in the toilet, turns the water blue and masks the smell after you wee. 
 
Their results found that the biggest barrier to flushing less might not actually be habit, it might be worrying about what other people think.

In the study the researchers recruited 20 adults and gave each a dispenser containing 70 Wizso pellets. 
 
For one week, participants used the pellets at home as part of their normal bathroom routines. 

Drop one into the toilet and it dissolves, colouring the water blue and releasing a fragrance designed to mask odour. The idea is that after urinating, you leave the toilet unflushed without the usual yellow appearance or smell.

At the end of the week, researchers interviewed each person for 40 minutes, asking when they flushed, when they didn't, and how they felt about leaving the toilet unflushed.

Overall, participants found the pellets easy to use.

The blue colour was surprisingly important. People associated it with bleach and toilet cleaning products, making an unflushed toilet appear cleaner.

People living alone were generally comfortable not flushing. Many were also happy doing it around partners and family.

However, when guests arrived, the flushing returned.

People worried that visitors might see an unflushed toilet and think they were unhygienic.

Female participants identified that seeing menstrual blood often prompted an automatic flush regardless of their intention to save water.

The researchers suggest that social expectations may actually be a bigger barrier to flushing less than the habit of flushing itself.

New Zealand is currently experiencing a strong El Niño, which is expected to influence our weather through the coming summer, bringing unusually dry weather.

That doesn't mean we're definitely heading into a drought, but it does make the humble toilet an interesting place to look for savings. 
 
A toilet flush uses betwee 4–13 litres of drinking-quality water, so at several flushes a day, that's a surprisingly large amount of treated water being used simply to carry away urine. 
 
The study highlights something fascinating about environmental behaviour.  Sometimes getting people to conserve resources isn't about convincing them to care more. 
 
It's about understanding, what actually stops them from changing their behaviour and designing around it.

In this case, apparently one of those barriers is not wanting your dinner guests to think you forgot to flush. 

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