In writes:

[snip]

If your convinced the new flapper is sealing OK, you could test for a
leak in the tank-to-bowl seal.
1. Shutoff the cold water line valve.
2. Flush the toilet normally
3. Some water should remain in tank up to the lip of the flapper seal.
4. Add a small bottle of red food coloring to the water in tank.
5. Wait awhile to see if red water shows up in bowl.

We had a really hard to diagnose similar problem. Yes,
thanks to the "food dye" test, we confirmed that water
was slowly seeping from the tank into the bowl.

After much agonizing work, including removing the unit,
separating the tank and the bowl, putting it back
together, etc., etc., we discovered that...

.... that the gasket between the tank and bowl
had disintegrated enough that water was seeping
through it and into the bowl.

Fortunately not onto the floor.

Solution: I stopped by the local shoe repair
place, picked up a 5 inch square of rubberized
material, cut a hole in it, and used it as
a replacement "O ring".

(Any similar material would have worked; the
shoe place was the most convenient).

What caused this?

We were using a pseudo chlorine tablet
in the tank for sanitary purposes (yeah, save
me the arguments about whether they work), and
that little bit of chlorine ate away at
the gasket.

If you go a'serch'in for:

"chlorine tablets eating away toilet gaskets"

you'll find lots of stories..

(if you're not using these then the chances
of an "o ring" degradation are slimmer, but
still could behappening).

--
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