Independent studies show that the energy used to heat the shower water is by far the largest environmental and climate impact of showering - not the water use itself. Furthermore, the studies show that from an environmental and climate perspective, recirculating gray water in showers is often negative compared to letting the water management be handled by today's existing high-efficiency infrastructure (clean water plants, distribution systems and wastewater treatment plants).
Therefore, Enduce focuses on reducing hot water consumption (the energy used to heat hot water) and not on recirculating water.
In a detailed study, we have examined the resource consumption of showering from a system perspective from water source to wastewater treatment plant, based on available research. The analysis shows that more than 96% of resource consumption is used to heat the shower water, while water use accounts for only about 4%.
In the absence of freshwater supply, where the water source is seawater (3.5 wt% NaCl), there is an additional 4 percentage points of resource consumption for tap water production and desalination - and the resource consumption for water production and wastewater treatment for showering accounts for a total of about 8 percent of the total resource consumption for showering in comparison with the heating of the water, which accounts for about 92 percent.
Source: Erika Wallén, Livscykelanalys av dricksvatten - en studie av ett vattenverk i Göteborg, 1999; Pratima Singh et al, Energy pattern analysis of a wastewater treatment plant, 2012.
