I ordered a new mechanism($75) and then had it installed ($120) but now it holds water really well and in fact more water than before is in bowl! When I looked at the NEW mechanism, it looked like it did not close completely but it hold the water really well. When older mechanism was looked at, nothing could be found to be the problem, but it did not hold water. It is a piece of plastic that is on a spring, that when the pedal is stepped on it pulls the plastic piece back. IT IS NOT a RUBBER gasket, it is plastic so god knows how long it will last but fixed for now!! Thanks for all the suggestions!!!