How do 1.6 GPF toilets differ from older model toilets?
Since a 1.6 GPF toilet is designed to flush with less water, you'll notice all the water does not leave the tank upon flushing. You'll also notice the water spot in the bowl is smaller, since less water is needed to operate the toilet efficiently. The toilet will operate optimally if all contents are placed within the water spot of the bowl, and not on the china sides.