I installed my new Toto Drake last Friday and have a leak at the left bolt holding the tank to the bowl. The strange thing is that it only leaks about 2 or 3 times per day, never after use, and will sit perfectly dry for hours then leak some only to remain dry for another 6-10 hour period. I put a newspaper under both sides so I could monitor any leaking problems that might occur. When the toilet leaks the water will cover most of the newspaper (folded) but rarely enough to soak through to the floor. Just trying to give you an idea of the amount of water we're talking about.
Prior to installation I lightly sanded the inside where the bolt goes. I've removed the tank and reinstalled a new washer using a very light coating of plumbers putty. Over the past few days I've tighten down both bolts (a little on each side at a time) to where I'm getting uncomfortable about over tightening. All of this and the leak has happened since day one.
Two things I noticed that may be worth mentioning. First, the raised area inside the tank where the rubber washer goes is somewhat off center to the hole. Also, my Toto came with only one rubber washer and my dealer gave me some spares, all of which are slightly smaller than the one with did come. Not much smaller. In fact just looking at them you might think they were the same size, but I did notice and side by side its easy to see.
Any ideas on what more I should do? At what point do I return the tank or have I reached that already?
I took the tank back to the dealer and while waiting for the new one we discovered and imperfection on the bottom. An indentation in the porcelain located at the flush value nut was apparently preventing a seal and causing a small leak.
The new tank is leak free after 24 hours. The new Toto is great.