Thanks for the info. Rather than take any chances, I replaced the fill valve and the flapper with Korky products mentioned in this thread. Seems to be working - will monitor for a day or so, but hopefully problem is taken care of. While it might have been the flapper alone, for another $10 I felt more comfortable replacing both parts.
WHile not too common, sometimes the flapper seat is not tight enough to the tank, and it can leak around that seal. If the new flapper doesn't resolve it, tighten the flapper seat a little.
Important note - I'm not a pro
Retired Defense Industry Engineer; Schluter 2.5-day Workshop Completed 2013
Well, this toilet is still causing problems, and finally got around to have some time to play with it today. Ended up having a plumber friend come over as well. Still seems the problem is from either the flapper - which now has the Korky 3060 in there, or the flapper seat, which I tightened down per the suggestion here. I notice there is a bit of play with the flapper, and if I put light pressure with my finger on the flapper during the refill the tank fills up. Without the pressure the tank will not refill. And once filled up, it will lose water slowly and then you occasionally here it refill. My friend said I should stick with the Toto flapper for this toilet, which at this point I may try again. My only other thought is perhaps some defect in the flapper seat preventing a good seal with the flapper? I am going to try Toto again and see what there thoughts are on this. The toilet and its parts are just too new to keep having these issues, when no other toilet in the house does, and both of my other toilets are Toto's as well.
Maybe brillo the flush valve seat.
Maybe look at how the chain is pulling the flapper up. Sometimes, we see people say that the flapper gets pulled up off angle, slides to one side of the posts on which its "wings" attach to the overflow riser, and then doesn't seat straight down. Sometimes, bending the trip arm so there's a straight pull-up motion allows the flapper to sit back cleanly in the valve. Also, because the Supreme is a lowboy, you might not have as much water in the shorter tank to press down on the flapper, making it more important that it drop back down cleanly.
These are some random thoughts. I would definitely contact Toto, and get them to send you a flapper under warranty and give you any other tricks to get back in business. We're a pretty good repository here, but I have seen where they come up with a solution and it works. Just try the 888 number on their web site. I have never had a problem getting an answer within a couple of rings, and friendly technician on the phone shortly thereafter.
You might also just get them to send you a new flush valve/overflow riser, and if none of this works, install that and see if the flapper doesn't seat better. They're very liberal about sending out parts to make customers happy.
Let us know how it goes.
Last edited by wjcandee; 03-25-2013 at 06:36 AM.