Eljer 525 flapper - American Standard 4112.016 Cadet Toilet Tank w/Coupling Components & Tank T

this is a case that dictates you replace the flapper.

Make sure the flush valve is closing properly and that the water level is not set too high causing water to enter the overflow tube. If the flapper seat is damaged and cannot just be be cleaned, you can add a new seat right over the old one. Fluidmaster sells them for just a few dollars. Most hardware stores have them - Home Depot and Lowes stock them.

Remove the tank. Remove the flush valve and replace with a new flush valve kit. May need to change tank seal also.

Make sure the chain to the flapper is loose when the flapper is down and that the handle when it goes through the toilet is free moving.

Hi,
Change the flapper with a generic one that will fit that toilet... the OEM flapper is **** and it does not allow for a good flush either...

heatman101

Hi Guy they have a hole in the flapper with air pocket that casues them a problem, you can buy aa flapper wth a chain on it that has a float on the back of the flapper valve so you can adjust it to work right. my experince has been to put the float right up aagainst the back side of the flapper. they cost $3.99 at any hardware store.

flapper valve leaking check for build up or debris if clean check adjustment or replace flapper

lift off cover and shorten flapper to handle chain/rubber connection flapper not opening all the way

Not being a plumber by trade I don't want to bad mouth what your plumber had to say but there may be other things to consider.
If the toilet does not flush directly into the main drain there is the possibilty that the coupling between the main drain and the toilet drain is under-sized which could cause reduced water flow and your toilet not flushing completely.

Replace flapper, it is worn out.Turn off water valve. Flush toilet, remove flapper. Then replace flapper, adjust chain to same size as old one, then turn water back on.