Why won't my toilet tank drain completely?

A little background info. My toilet is 5 years old. The old flapper was sticking in the up position. I removed it, scrubbed the scum/residue off of it and re-installed it. This solved the sticking problem but then it leaked and let water run out of the tank. I determined it was deformed and purchased a new flapper. I installed the new flapper and it seals great which solved the water leak problem but now when I flush the toilet the new flapper won't stay up long enough to let more than about 25% of the water out of the tank. This results in incomplete flushes. I've adjusted the chain to every length possible from tight to the point it had no slack to lots of slack and it barely raises the flapper. Now I have the chain set so there's just a small amount of slack so the flapper seals good but when I flush the handle the flapper opens fully in the up position. Problem is as soon as water starts to run out of the tank the flapper slams shut. What's the cause? Thank you.

 

The bottom of the flapper should have a hole in it. Be sure its not full of water.

 

Hi,
1 Do you have an adjutable flapper? It has sort of like a dial on the flapper.
2 Did you install the flapper correctly? Most newer toilets have "ears" to hook the flapper to. Most flappers come with a donut and rubber hinges that fit on the "ears" if your toilet has the ears you must cut the donut off. Make sure to leave the hinges on.
Good Luck Woodbutcher

 

Sounds like you installed the wrong flapper for the toilet..

Whats the make and model toilet? Some need to reinstall the type with the dobber if thats what it had...

Especially kohler toilets need OEM. Aftermarket types never seem to work...