On Mon, 08 Apr 2013 15:56:50 +0000 notbob wrote:

Over time, this has caused heavy brown deposits (lime?)
in the bottom of our porcelain crapper.

I don't know much - so go by what others say ... but if it's brown rust,
you might get away with phosphoric acid based solutions.

By way of example, here's a picture of a brown-stained toilet at my
sister's house that I put some naval jelly on this weekend:
http://www2.picturepush.com/photo/a/...g/12641055.jpg

I don't have a followup picture yet because I told her to let it soak for
a while and then flush the toilet - so I will need to return to her house
to see whether it worked or not.

BTW, I don't know what the brown stains are, but they don't clean easily.

The bleach did not work. My sister said she had scrubbed already, so I
didn't even try to scrub them. I'm hoping the phosphoric acid, left on
for an hour or two, will have done the trick by the time I return.