Snake line from under sink Remove P-trap and snake line then test line to insure it is flowing With customer approval ran 25ft drain machine and cleared blockage after blockage was cleared ran water to insure it was flowing made customer aware with old galvanized piping there is no guarantee that issue will not return made customer aware to use garbage disposal as less as possible gave customer price to replace drain line with pvc and made them aware that price is good for 90 days