A few years ago we had need to "see down the pipes" to locate a terrible obstruction. We contacted the Laconia "Mr. Rooter" and he arrived with a special Camera Rooter! Sent it down the line and had a clear view of the problem! Helped make the determination of how to proceed with the least amount of disruption!!!!! I would recommend you call him - his number is 524-8484. He's the man for the job. Wish I could remember his name, too, but alas, my age is showing!
Good luck, and come back and let us know what happens.