HARD WATER STAINS
During home watch visits a house can sit for two weeks to a month without any movement. Between the higher temperature of the interior home and the evaporation of water in the toilets sometimes a hard water ring forms in the toilet. This can happen even if water is sitting to the proper water level.
An etching affect happens and even if you scratch the etch line you cannot remove the ring around the toilet bowl.
This procedure might help. Turn the water valve OFF. Flush the toilets so very little water enters the bowl. Squeeze a good amount of "whink" Rust Stain Remover around the rim and ring line. Wait 5 minutes and brush with toilet scrub brush that has good scrubbing power. Turn the water back on and flush. This should help out a lot. I take this with me on my home watches in case I need a little boost. Let me know how it works for you.