Drake tank gasket can leak

A while ago, I posted a question about whether the Toto Drake tank gasket can leak. I suspected it after experiencing a slow leak and efforts to sand and seal the tank bolts didn't seem to help. Previous post
Well, it CAN! After pulling the tank for the upteenth time after a time gap because of remodeling, there were clear water stains on the gasket. Water was leaking from where the gasket touches the tank.

I decided to fix the problem once and for all with some silicone caulk. While tightening the tank down for hopefully the last time, I thought I would stick my fingers through the flapper hole and feel how the gasket was tightening down. Surprisingly, it was very uneven. I felt a lot more gasket toward the front of the tank than toward the rear. I felt certain the gasket was centered before I started tightening. I loosened the tank bolts. Had to work quickly before the silicone set. The tank gasket felt centered with the tank bolts loose. I thought a little bit and began to wonder if the front-back tilt of the tank was affecting how the gasket tightened down. I thought I had it vertical but I pushed the tank toward the back wall and started tightening the tank bolts again. This time, the gasket felt more even front to back. Better, but not perfect. And the tank contacted the bowl at the rear first rather than the front as it had before.

My slow leak is gone and the Toto is in "full service".
- The Drake CAN leak around the tank gasket. I saw visual proof of it.
- Make sure the tank is vertical before tightening the tank bolts. Feel the gasket through the flapper hole to make sure it is as even as possible.
- If all fails, silicone sealer works.

Yes, we find that putting the tank on straight is a good way to go.
Always push the foam seal onto the outlet of the tank, before setting the tank onto the bowl. Keep the tank aligned while tightening.

There is the rare occasion when the inside of the tank is cast rough enough where the seal just below the flush valve will not seal.
A little emory cloth will smooth the porcelain and it can be reassmbled.
If find this to be very rare. Maybe one in a hundred.

I followed up on a Drake tank installed by another plumber that was loose today, 10/22/2008
The tank nuts were "finger loose",
I took out a wrench and tightened them "wrench tight"
No more loose and wobbly tank.