The water efficiency of toilets in Australia has increased significantly since the 1980's due to the development of the dual flush toilet, and the progressive reduction in average flush volumes with each new model. The accurate modelling of the average efficiency of toilets is very important as a component of demand forecasting, which itself is at its most powerful when it is disaggregated, and based on end use modeling. The stock mix of toilets has been modeled and calibrated using data from two yearly surveys of the toilet stock that have been undertaken since 1992. A lognormal function was found to most accurately represent the declining share of single flush toilets in the mix. The introduction of dual flush toilets has had a significant impact on total toilet demand in Australia. By 2007, the savings already achieved amount to 214 GL per year. An accelerated retrofit program would save an additional 79 GL per year.

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