Small hole in flush path -- what is its function?

[Awake]

No, not the one you are probably thinking of (inside the bowl); this is a small hole in the area where the tank joins with the toilet. Here is a picture with an arrow pointing to the hole in question:

When I removed the tank, this was plugged with a blob of caulk. Initially I thought that must have been a mistake of the original installer ... but then I got to wondering if that is actually meant to be plugged, for some reason.

Can anybody shed light on the purpose of this hole, and whether it should be plugged or not?

 

[Reach4]

I am thinking that it was supposed to be plugged. I have not felt that brighter white material to see if it was hard. I have just presumed it was hard. Are you saying that remaining bright white material is soft like caulk?

 

[Sponsor]

 

[Awake]

Yep, like a blob of silicon caulk. Do I take it that you have seen this hole plugged in toilets as well? If so, that makes me think it needs to stay plugged for some reason ...

 

[Terry]

My first guess is that it's a steam vent.
A void in clay will break in a kiln. After it's removed, they may have plugged the hole.

 

[Awake]

Which means, I think, that I'd better plug it back up!

 

[hj]

If correct, it should not make any difference what you do with it.

 

[DonL]

That is the freeze plug.

Sounds good. lol

 

[hj]

IF the toilet freezes, the "freeze plug" will be useless.