After watching this video, it makes me want to clean it because its easy without any scrubbing.
There can be a lot of rust, lime, and other mineral deposits that build up.
Hold the handle down to get as much of the water out as possible.

Image by Andrea Jean Cleaning via YouTube
Then, flush the toilet to see the results.
Continue to watchAndrea Jean Cleaning tutorialon YouTube for the full instructions and details.
Im impressed by how a single product can clean up all of the dirtiness easily.

Its incredible how this works, and she tried the bleach method, but it did not work.
