On Sat, 15 Jan 2011 21:45:24 -0500, LSMFT wrote:

MikeL wrote:
I had a toilet tank that needed a new flush valve, so I picked one up
at Lowes, a universal plumb pak....no matter what I did, everytime I
put the tank back on, a small leak happened around the nut of the
flush valve on the bottom of the tank. I even filled it at the kitchen
sink and watched to see if it would leak, but when installed, a few
hours later it was leaking on the floor. I had another tank just like
the first and put a new flush valve on it and lo and behold, a few
hours later, it leaked also...for the life of me I really don't know
what I was doing wrong. These were toilets in a mobile home...a 'oso'
model(?) Don't know if I was tightening the nut too tight or didn't
have it tight enough...any thoughts?
I finally purchased a new tank and put it on, no problems, as of right
now.

BTW...on the tank to bowl gasket, does the gasket have to fit over the
threads and the nut? or just the threads only?
thanks, Mike

In the first place you don't remove the tank to replace a flush valve.

If you are replacing the entire flush valve on an American Standard
throne you DEFINITELY need to remove the tank, as the nut that holds
it on is between the tank and the bowl.
If you are only replacing the water control unit, or the flapper
portion of the flush valve you can do it while assembled.