There can be many causes of a blocked drain. But while drain jetting may remove a blockage it is usually impossible to find out what caused the blockage unless a CCTV survey is carried out.
A CCTV survey is the only definitive way a drain inspection company will be able to determine the cause of your drain blockage or the condition of the interior of your pipes. The camera equipment used by drainage experts will be able to examine the internal structure of the pipe in detail and relay the images to a computer where the drainage expert will be able to view them in real time.
A detailed report can be made on the condition of the drainage system with any recommendations made by the drainage company on what needs to be done to bring the pipe network up to standard.
It may be the case that your drainage system is in a good state of repair and the blockage, once removed, might have been the only problem. It could be the case however that the drain needs to be relined or a section of the drain will have to be repaired. In any of these cases your drain inspection engineer will be able to help.