I've put two new flappers into my Toto toilet (Carollton model) to deal with an intermittent leakage from the tank to the bowl and still the problem continues. A call to Toto's customer support suggested that there might be smutz on the rim of the tank's drain hole so I scrubbed it with a scouring pad but no improvement.
After flushing, the tank fills normally and then some time later, the tank is heard filling up a bit more in response to leakage from the tank into the bowl. This continues indefinitely. The flappers were pink flappers bought at a plumbing supply store for this model toilet and represented to me as Toto brand, although they were not in a labelled box or wrapper. The Toto rep verified that the pink flapper was the correct one for my Toto model.
Anyone have any suggestions?