Modelling Preferences for Non-Conventional Water Sources for Toilet Flushing: A Discrete Choice Approach

Andrews, Cameron

Modelling Preferences for Non-Conventional Water Sources for Toilet Flushing: A Discrete Choice Approach

Thesis / Dissertation

2026

Publisher

University of Cape Town

Department

Department of Civil Engineering

Faculty

Faculty of Engineering and the Built Environment

Abstract

Urban water systems in arid and semi-arid regions are increasingly stressed by climate change and rising demand, highlighting a need for decentralised and alternative supplies. While the technical feasibility of options such as desalinated seawater and recycled water is well established, household acceptance remains a key constraint, particularly for its household applications. This study investigated household preferences and underlying decision-making rules for using non-conventional water sources to flush toilets in the coastal, water-stressed context of Hout Bay, Cape Town. A labelled discrete choice experiment (DCE) was developed to compare partially treated seawater, recycled water, and drinking water as flushing sources, with attributes reflecting water aesthetics (stain, colour and odour), cost implications, and disposal practices. The experimental design presented six choice tasks to each respondent and was administered via intercept surveys, following piloting and refinement. A latent class (LC) model revealed two behavioural classes, namely an environmentally conscious group, insensitive to cost and aesthetics, and a cost-conscious group whose acceptance was strongly shaped by cost changes and the colour of the water, alongside support for improved disposal practices. Overall, the results indicate that toilet flushing is a viable entry point for household acceptance of non-conventional water sources, with partially treated seawater emerging as a particularly promising option in a coastal community. Implementation strategies should therefore be framed in relation to affordability for cost-sensitive households and environmental benefits for environmentally oriented households.

Keywords

urban water systems

climate change

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