How do i clean the stains from my porcelain toilet bowl?

use clorox

try Coca cola with dishwashing liquid.

or baking soda and white vinegar.

i did mine (in the bath) and it worked.

It could possibly be hard water deposits, I have dark areas in my toilets, too and found out it is from the hard water. I have to use a sharp object like a flat head screwdriver to chip it away when the bowl is empty.

it is not a hard surface, it looks like a stain, sometimes a toilet brush works, but the area under the bowl lip is impossible to clean.

i wonder if i put straight bleach in the tank along with the water, if it will help.

You can use a pumice stone. It will rid all hard water deposits.

My husband used a pumice stone and now there are scratch marks on bottom of bowl. I have tried bleach, baking soda to fix but? Can bottom of bowl be painted? If so with what, I have brushes....