Toilet Flapper Slams Shut. fixing a toilet flapper that won’t stay closed will depend on what the issue is. The flapper has to come up past vertical, so that it's out of the way for the full flush.
Use a clean sponge to remove the flapper hinge. The time saved will outweigh the cost. my toilet is flushing as normal but the toilet flapper slams shut loudly now.
SureFit 504 Universal Toilet Flapper, For Use With Flush Valves With
Flush the toilet to empty the tank. Use a clean sponge to remove the flapper hinge. too short a chain length and you pull that flapper all the way up, possibly getting it stuck. There are occasions when the ball float and the arm are not appropriately positioned.