Your shampoo routine could be driving household water waste, according to new study

Everyday shower habits, such as applying shampoo or pausing the water while washing, are driving up water waste, argues a new study from the University of Surrey.

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Published in the Journal of Environmental Management, researchers found that showers account for between 25% and 45% of indoor household water use, making them the single largest contributor to domestic water consumption. Yet policies aimed at reducing water demand focus on technology, such as efficient showerheads or pricing mechanisms, rather than understanding behaviour inside the shower itself.

The findings show that instead of factors such as gender, household size or home type, in-shower routines and product use play a far greater role in determining shower length.

Researchers analysed shower behaviour in 319 German households using smart sensors installed in bathrooms. Over 40 days, the devices recorded 8,550 shower events, capturing duration, water pauses and environmental conditions. These data were then combined with time-stamped post-shower surveys to link observed behaviour with information on demographics, product use and hair characteristics.

It turns out the biggest drivers of water use are not who you are or where you live. What matters most is what you actually do in the shower. Small routines such as applying shampoo twice or letting the water run while lathering can extend shower time far more than people realise. Dr Pablo Pereira Doel, Human Insight Lab co-director; Fellow at the Institute for Sustainability; Visiting Fellow, Center for Tourism Research at Wakayama University (Japan)

The analysis showed that showers involving two or more shampoo applications were around 27% longer than those with a single application. Similarly, showers with three or more pauses in water flow were around 20% longer than those with no pauses (and 28% longer than those with a single pause). Younger and middle-aged adults also tended to shower longer than people over 50.

Water hardness also played a role. Showers in areas with softer water lasted about 23% longer than those in hard water regions, possibly because softer water produces richer lather and a more comfortable experience, encouraging people to linger.

The researchers argue that these insights could help design more effective strategies to reduce water use. Instead of focusing solely on technology or pricing, interventions could target behaviour during showers, such as encouraging single shampoo applications or prompting users to turn off water while lathering.

If we want to reduce household water consumption, we need to design solutions that work with people’s habits rather than against them. Behavioural nudges, smarter feedback devices and better product design could all play a role in helping people use less water without sacrificing comfort. Dr Pablo Pereira Doel, Human Insight Lab co-director; Fellow at the Institute for Sustainability; Visiting Fellow, Center for Tourism Research at Wakayama University (Japan)

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Note to editors

Dr Pablo Pereira-Doel is available for interview. Please contact: mediarelations@surrey.ac.uk to arrange. 
The full study has been published in the Journal of Environmental Management