A pellet that dissolves in the toilet, turning the water blue and masking odour after urinating, could help us all save water, according to a first-of-its-kind study from the University of Surrey. The research, which investigated the use of the commercially available product, Wizso, found that households are more than willing to skip flushing, but only when nobody is looking.

The small but unique study looked at 20 adults living in the UK who agreed to try using the pellet before or after flushing for a week and were then interviewed about their experience.

Participants told researchers that the blue water that the pellet created was reassuring – with many associating the colour with cistern blocks and bleach. Reactions from the participants were more cautious when they had guests, or where there were visible signs of an unflushed toilet, due to concerns that others would judge them for breaching hygiene norms. Another stumbling block came from female participants, who said the sight of menstrual blood prompted them to flush automatically, whatever their environmental intentions.

Overall though, the pellets were well received, with participants finding them easy to incorporate into their usual routines, despite ingrained habits for flushing after use.

Sophia Shaw-Brown, lead author of the study from the University of Surrey, said:

“We think that social expectations – the fear or stigma of what people might think of them if they were “found out” to not flush – are a bigger problem than the habit of flushing itself. We found that our participants who lived alone were more than comfortable with leaving the toilet unflushed, and most were comfortable around partners, children and other family members. However, normal flushing resumed when guests arrived.”

Almost a quarter of domestic water use in the UK is down to toilet flushing and each flush uses between four to 13 litres of drinking-quality water (other countries such as Hong Kong use seawater for this). It is estimated that people flush six times a day, which adds up to 25 to 80 litres per person per day caused by flushing alone.

The UK water industry wants to cut average personal use from 145 litres a day to 110 litres, against a projected daily freshwater shortfall of five billion litres by 2050.

Professor Benjamin Gardner, senior author of the study and Professor in Psychology at the University of Surrey, said:

"Water scarcity is a huge problem in the UK, but people will probably forget about the need to save water when it starts raining again. Innovative new solutions are needed to help people save water all year round, as part of their everyday routines. Although there will undoubtedly be situations where people don’t want to leave their loo unflushed due to embarrassment, these pellets provide an easy way of saving water overall, by reducing the number of times we need to flush after peeing.