Arrived on site per customer complaint of drains backing up in units 10, 11 and 12. Upon arrival I found a clean out for #10 to be full of sewage. Trailer #9 is flowing freely and not having backups. Provided customer pricing to attempt to drain clean through an outside clean-out. Customer accepted pricing. Attempted to run my 300 machine down through the outside clean-out. After multiple attempts of working my cable back and fourth I was unable to clear the obstruction. My cable would begin to bind very hard. Ran camera down the line and the camera would go completely black right between 6-8ft. Attempted to locate underneath the trailer and was unable to due to their be limited access underneath the trailer. CPI had previously been out to replace the section of piping between #9 and #10. We then ran our camera down the clean-out on the opposite side of the trailer #10. Found our newly installed piping to be clear and flowing freely. Informed Jeff of our findings. CPI will be providing