For such buildings, the witness said that one could have hot water stored in cisterns on roofs. Have you ever considered having two water systems: one for drinking water and one for other uses such as flushing toilets and cleaning floors? Treated water is very expensive whereas untreated water is much cheaper. It is certainly not necessary to use treated water for flushing toilets or things of that nature.
On March 10th, 2009. See this statement in context.