Showering is one of the most water-intensive behaviours in urban households, accounting for 20–30% of water use. Real-time feedback from smart devices has been proven to significantly reduce water consumption in showers. Still, it is not known whether these devices have spillover effects on other water use behaviours. For the first time, we provide empirical evidence for a significant and negative within-domain spillover effect from the use of such devices, showing an increase in water use in other activities by 2.5% per day per household. Up to one-third of conservation effects are eroded by such spillovers, resulting in a two steps forward, one step back situation. Overall, however, net water use is still reduced by 4.7% in the 385 households that were observed. This study points out an important behavioural limit on the use of such smart shower devices and suggests that such use be accompanied by informational or other campaigns to reduce the large negative spillovers.
