Welcome to Mrs. Clean's forum. We can definitely help you out!
I know that you have tried liquid cleaners, but you can either try them with the method listed below or skip to the section on pumice stone. Please read all directions first because you must use a pumice stone properly to avoid scratching the porcelain.
To remove those toilet bowl rings, you can use either full strength white vinegar, a commercial mineral deposit remover, or if the deposits are really heavy a pumice stone will do the job quickly.
* First, turn off the water supply to the toilet.
* Flush the toilet to remove most of the water.
* Soak some paper towels with full strength white vinegar and position these on the toilet bowl rings
* Let the towels sit for several hours. The mild acid in the vinegar will work to dissolve the mineral deposits.
* Scrub the ring with a green scrubbie or a nylon brush
If the vinegar does not do the trick, repeat the process with a commercial lime scale remover (you can purchase this at the grocery store)
If the vinegar or hard water lime scale remover it just not getting rid of the toilet bowl ring, you can use a pumice stone. Pumice is all natural volcanic rock that is a very good abrasive that gently dissolves as you use it.
We use pumice stones ourselves (at Mrs. Clean) but it takes a delicate hand, and it must be done carefully to avoid scratching the porcelain surface of the toilet bowl. Lots of water, and gentle consistent pressure is the key here.
* You can purchase a pumice stone from the grocery store
* Moisten the pumice stone (oh come on, just dip it in the toilet water- You have gloves on right?)
* Rub the pumice stone on the toilet bowl ring, using gentle consistent pressure until it disappears.
* Keep the pumice stone wet, re-moistening frequently
* Use a green scrubbie to finish up.
This should do the trick and your rings should disappear! For other great bathroom cleaning tips visit this page on Mrs Clean.
http://www.mrscleannw.com/tips/shower-cleaning.html
Good Luck.