While we are successful in removing the majority of stains, there are many variables to this, such as the age of the stain or if you have tried to remove it yourself using a detergent based product that can set the stain even more.
Some stains when set can discolour the fibre of the carpet. Particularly in Wool rich carpets that have more absorbent fibres, stains may be permanent, however, that is the worst case scenario.
Even if that stain cannot be completely removed, using a detergent-free rinse and the appropriate solution for the stain can usually achieve a satisfactory result.