I have now that I found this site a champion toilet. Didn’t even know what it was until I run across this site. It was problematic ever since we bought the house a few years ago. It was preinstalled in the house. I don’t mind the noise as it is great to not have to plunge as with so many of the new fangled low flow units. I made a few adjustments to it at first and seemed to work nicely. Now It has began to run on and on draining the tank in only a few hours. Taking it a apart and finding the huge hole (4” or whatever it is) was a bit of a shock when no parts are available and even a net search it is nearly impossible to find anything. After taking the tank off and not having parts for repair I made a few adjustments that may be a temporary fix and some of you may find helpful. The little red/orange seal as others have mentioned had developed blisters. I removed the seal dried everything off and pierced the blisters with the point of a small pair of scissors. I squeezed the water out and put a second hole in the blister to help alleviate re-expansion with water. I reseated the seal on the plunger/piston. I coated the whole thing with petroleum jelly and re-assembled the toilet. The petro jelly also will help disperse water and seal the holes in the blisters. I also inverted the washer so the deformation of the rubber is opposite what it was before helping the seal to contact its mating point and form a proper seal. I would think the petro jelly would assist in keeping this seal in place for those who are having problems with it slipping off. Aslo the seal has a pretty tight fit in the groove of the plunger, make sure it is well seated. (as I mis-seated it a couple times before I got it right). This was about 24 hours ago and I have not lost one drip of water through the valve yet. I am not sure how long this will hold up but maybe until I can get some new parts located. The other problem is the huge sponge washer/seal from the tank to bowl seal. Can’t find one of those either.