Odd toilet leak problem here for anyone who wants to take a shot at a hard
to diagnose condition.

Symptom:
Toilet tank leaks into bowl, causing very frequent (every 15 minutes or
so) top ups of the tank. The leak is really bad; in reflective light,
water in bowl ripples noticeably after tank finishes filling.

The tank is not overfilling, water is not entering the bowl via the
overflow tube.

Obvious likely cause is the flapper. Replaced. Problem persists,
unchanged.

Next. Using gently duty scrunge, clean seal that flapper seats into.
Problem persists, unchanged.

Next. Try light coat of plumbers grease on flapper and seal. Problem
persists, unchanged. Try heavy coat of plumbers grease on flapper and
seal. Problem persists, unchanged.

Carefully inspect fill tube to be sure it is not cracked and leaking from
tank into bowl. No cracks or seepage found.

The last possible cause (leaving out cracked porcelain) is the rubber seal
between the tank and the bowl.

I worked a lot of overtime this week, and I haven't had time to make
another parts run and remove the tank.

As luck would have it, the manual shut off valve leaks when closed. This
means that when the water supply is shut off, the tank slowly (about one
hour) fills itself to the full normal level.

Here is where it gets weired. When the tank fills slowly through the
leaking water supply manual shut off, the tank does not leak into the
bowl. No leak at all.

WTF!? Wouldn't a leaky seal leak whether the tank fills very slowly or at
a normal pace? Why would that make a difference?

--
Tony Sivori
Due to spam, I'm filtering all Google Groups posters.