A Shower’s Smallest Habits May Be Driving Much More Water Waste Than Expected, Study Finds
The length of a shower may depend less on who is standing beneath the water and more on what happens during the routine itself, according to new research from the University of Surrey. Everyday actions such as applying shampoo more than once, pausing the water while washing, or allowing the shower to run during lathering were associated with substantially longer shower events—and potentially much greater household water consumption.
The study, published in the Journal of Environmental Management, examines showering at the level of individual events rather than relying solely on averages or people’s estimates of their behaviour. Showers are estimated to account for between 25% and 45% of indoor household water use, making them one of the largest controllable sources of domestic consumption. Yet many water-saving policies focus primarily on hardware, including low-flow showerheads, smart meters and pricing, without examining the detailed routines that unfold inside the shower.
To investigate those routines, researchers monitored 319 households in Germany using smart sensors installed in bathrooms. Across more than 40 days, the system recorded 8,550 shower events, capturing how long each shower lasted and whether the flow of water was interrupted. The researchers then combined these measurements with time-stamped surveys completed after showers. The surveys provided information about product use, hair characteristics, demographic factors and the environmental conditions associated with each event.
This combination of sensor data and self-reported information allowed the team to compare measured behaviour with the actions people said they had taken. Such event-level monitoring can reveal patterns that are difficult to detect through questionnaires alone, because people may underestimate shower duration or fail to remember how often they paused the water. By linking each survey response to a specific recorded shower, the researchers were able to examine how individual habits corresponded with changes in shower length.
The strongest associations involved shampoo use and water pauses. Showers in which participants applied shampoo two or more times were approximately 27% longer than showers involving a single application. The result suggests that repeated product use may extend more than the time needed to distribute shampoo. It may also encourage additional rinsing, lathering or preparation, creating a sequence of small delays that increases the total duration of the event.
Pausing the water did not necessarily shorten a shower either. Events involving three or more interruptions in water flow were around 20% longer than showers with no pauses and approximately 28% longer than showers with a single pause. Turning off the water can reduce flow during the interruption itself, but repeated stopping and restarting may lengthen the overall routine. People may also leave the shower running while applying products, or spend additional time adjusting the water before resuming.
The analysis identified other, more limited influences. Younger and middle-aged adults generally recorded longer showers than people over 50, while factors such as gender, household size and type of home appeared to play a smaller role than in-shower behaviour. Water hardness was also associated with duration. Showers in softer-water areas lasted about 23% longer than those in harder-water regions, possibly because softer water produces richer lather and creates a more comfortable sensation that encourages people to stay under the stream.
Water hardness is determined largely by the concentration of dissolved minerals, especially calcium and magnesium. Hard water can make soap and shampoo lather less easily and may leave mineral deposits on hair or bathroom surfaces. Softer water can change the sensory experience of washing, potentially affecting how much product people use and how long they rinse. The study does not establish that water chemistry directly causes longer showers, but the pattern suggests that local environmental conditions may interact with personal routines in ways that influence water demand.
Because the research was observational, the findings show relationships rather than definitive cause-and-effect mechanisms. Participants were not randomly assigned to use one shampoo application, a particular shower routine or a specific water hardness level. Nevertheless, the scale of the dataset and the use of direct sensor measurements provide a detailed view of real-world showering. The results indicate that efforts to reduce domestic water use may be more effective when they address behaviour as well as technology.
The researchers argue that practical interventions could include prompts encouraging people to use a single shampoo application when appropriate, reminders to avoid running water while lathering, and feedback systems that show how long a shower has lasted or how much water it has used. Product manufacturers could also explore formulations that rinse more quickly or provide effective cleaning with less repeated application. According to co-author Dr Pablo Pereira-Doel, the most successful strategies will work with people’s habits rather than simply demanding that they change them. Small adjustments to familiar routines, supported by well-designed technology and behavioural cues, could help households reduce water consumption without giving up comfort.
Subject of Research: People
Article Title: Event-level modelling of showering behaviour in German households: Triangulating smart-meter, in-situ survey and contextual public data
News Publication Date: 30-Jul-2026
Web References: Journal of Environmental Management; DOI: https://doi.org/10.1016/j.jenvman.2026.130596
References: Pereira-Doel, P. et al., “Event-level modelling of showering behaviour in German households: Triangulating smart-meter, in-situ survey and contextual public data,” Journal of Environmental Management, DOI: 10.1016/j.jenvman.2026.130596
Keywords
Water conservation, shower behaviour, household water use, water waste, shampoo use, smart sensors, environmental management, water hardness, sustainable living, behavioural nudges
