Been running into a problem and have already found an acceptable solution. I still question though; when I replace some standard-looking toilet flapper with universal fit flapper from the supply house, why do the toilets flush more than once per lever pull? The flapper will stay upright until the whole tank is evacuated. As if the water is preventing the flapper from falling back down. I was having this problem mostly on Kohler toilets that weren't too old. I was thinking maybe I should buy the OEM flapper for each brand of toilet I run in to. I found an adjustable flapper that has sufficed for now. Any thoughts?