Sloan FLUSHMATE has introduced the FLUSHMATE IV pressure-assist 1.0-gallon/3.8-liter system. The FLUSHMATE IV flushes less than 4 liters per flush, saving 40-70% more water compared to gravity flush toilets. The FLUSHMATE vessel traps air, and as it fills with water, it uses the water supply line pressure to compress the trapped air inside. The compressed air is what forces the water into the bowl. So, instead of the "pulling" or siphon action of a gravity toilet, the pressure-assist toilet "pushes" waste out. This vigorous flushing action also cleans the bowl. Sloan FLUSHMATE.