Limescale mainly forms in toilets when a little water always runs out of the cistern. This then becomes noticeable as a white to yellowish or brown deposit in the toilet bowl.
Chemical cleaners are not necessary - home remedies are also excellent at removing limescale. In order to dissolve the lime, acids are needed - which are also found in natural home remedies. Acids in particular are ideal as descalers because they react with the calcium carbonate in the lime deposits and make them more easily soluble.