The only “dual flush” toilets I have heard about are the new ones that will not flush properly with the first flush, or older units that have been modified, or are in disrepair, and thus need two flushes to operate. The water conservation standards do not always consider the ramifications of the regulations. For example, a mandated low flow kitchen faucet often does not give the proper volume to operate a food disposer and thus will cause frequent stoppages. That same faucet when used to fill a sink bowl for dishwashing, etc., will use the same amount of water as a non-low flow faucet, it will just take longer to fill it. Low flow shower heads have to be designed with smaller and/or fewer openings so that the dynamic residual pressure behind the openings will be sufficient to provide a satisfactory spray effect.