How to fix toilet that doesnt flush completely

Fill the breather hole (1/8" hole) inside the flapper.This is designed to let air out so the flapper will sink. Now it floats longer letting in more water. 25%percent more in my case.

hello hans.... here is the link that has the info you seek. http://www.americanstandard-us.com/resources/technicalfiles/default.aspx?sw=high

Joe

I had this issue as well with my toilet. My chain was unattached and had been sucked down the drain under the stopper valve preventing the toilet stopper valve from completely closing and causing the water to continually run. After re-attaching the chain I noticed when I flushed the toilet that the handle did not rise again until I manually pushed it up. After readjusting the chain to a tighter position where the chain was not floating at all but instead holding the stopper valve in place I again flushed to check the reaction. This fixed the issue of the water continually running and also the handle not resetting itself properly.

Here is the steps I took to resolve my issue:

Step 1: Remove the lid off of the tank.

Step 2: Check to see if the chain coming from the Toilet Handle to the Stopper Valve is loose, unattached, or broken.

Step 3: Flush the toilet and check to see if the problem has been fixed. If not readjust the chain to a different position and flush again.

Step 4: If all is resolved replace the tank lid.

Other possible things to check:
Check the Float Ball to see if it's Half-way or more submerged in the water. If it is it needs to be replaced.

I hope this helps!

change and or adjust the flapper valve if the chain is to long flapper wont stay open long enough for the water to drain into the bowl

lift off cover and adjust =shorten length= between flapper and handle lever

Take off the top lid and look at the flush handle mechanism. You'll see a not that holds it onto the tank. Tighten the nut so it is snug. Don't overtighten it or you could crack the tank. Next inspect the chain that goes between the end of the flush handle rod and the flapper valve. It should lift the flapper all the the way up when you operate the handle.

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.

This is how it is meant to work!
Short push of lever for small flush, push and hold lever for full flush.

No you just need a new flapper for your flush valve. Its just a 2 minute job.