We have a partially obstructed sewer pipe -a new issue in a 50+ year old home. The plumber believes a length of the pipe has sagged and suggests jetting the line and a camera inspection - approx $1300. If he is correct, to "fix" the pipe would be excavation and replacement. I read about trenchless fixes where a replacement pipe was sent through the pipe, like a medical stent. The new pipe materials seem to be either PVC or some flexible material which is inflated. Has anybody had experience with this? Any other new technology rather than the big costs of excavation?