Install WaterSense® certified toilets
Older toilets use 13 or even 20 litres per flush. The new standard is 6 litres per flush. Two button toilets typically use 3 litres for a “small load”, and 6 litres for a “large load”. WaterSense® certified toilets use 4.8 litres per flush. A WaterSense® certified two button flush toilet would have an average flush volume of 4.8 litres per flush. Also, to be WaterSense® certified, the toilets have to flush well.
WaterSense® toilets are available at most hardware stores. If you are having a plumber supply and install the toilet, specify that it must be WaterSense® certified. There are many WaterSense® certified toilets available for $100 to $400.