The toilet is the biggest water-user in the average household. Water saving toilets can save thousands of gallons per year. Older toilets use about 3.5 gallons per flush while newer toilets use 1.6 gallons per flush. The difference can save around 12,000 gallons over the course of a year. Dual-flush toilets can save even more. They have two buttons: one for liquid waste which does a partial flush, and the other for solid waste which does a full flush.