Our toilet tank is draining a little from somewhere because it will refill a little every couple of minutes. I tried replacing the flapper and flushing mechanism, but it's still happening. The only thing left to change would be the seal between the tank and toilet... right?:confused:

Are you leaking on to the floor? If not then it's probably not the seal. Have you changed the flapper mechanism all the way down to the porcelain? Or just the flap? You should change the whole flap assembly as the replacements don't always seat right.

Let's try readjusting before we replace the flush valve.
Check the tank water level, it should be at the mark in the tank or 3/8 to 1/2" below the top of the over flow tube. Now look at the flapper, If it has wavey edges on the flat surface, replace it. The linkage between the flapper and the flush lever should have 1/4" play when the tank is filled. Also, check the small tube coming out of the top of the bakkcock and make sure it's connect to and draining into the white overflow tube. Pay attention to the linkage adjustment. Let me know. Tom

I am not sure if you have already done this but you need to install a whole new flush valve assembly.

Not the fill valve... the flush valve. If you have done this then you may have a problem in the installation of the parts you replaced. May need to start over again.

As GRT (hello fellow mass. Person) said... not the seal... would leak onto floor... not bolts as that would also leak onto floor. SO.. must be the seal at the flush valve... OR A DEFECTIVE FLAPPER. Also note that if this is just installed new flush valve assembly... you need to give the flapper time to seal to the flush valve assembly. Hope this helped.

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Sir you are correct, I was thinking of the tank gasket.

That tube that Tom spoke of must be connected to and flowing into the overflow pipe but it must not be stuck down into the overflow so far as to be below the water line. This will create a syphoning action after the fill valve shuts off and drain the tank back down to begin filling again. With a 2 minute cycle it sounds like this is what is happening.