No hydraulic impacts due to implementation of greywater was identified on catchment flows, according to research from Cranfield University.

“A simulation model developed in InfoWorks CS (Wallingford Software Ltd) was used to evaluate how river flows, sewer flows, surface runoff and flooding events may be influenced when grey water recycling systems of different number and scale are implemented in a representative catchment. The simulations show the effectiveness of greywater recycling systems in reducing total wastewater volume and flood volume,” wrote N. Bertrand and colleagues, Cranfield University.Water Science and Technology, 2008;57(5):741-6