Nifty............
I am a Plumbing Contractor and have been for over 20 years. I haven't heard of this proceedure. I would be concerned on the pipe having the correct fall to allow the debris to run from the house to the sewer tap at the street usuing this proceedure. Over the years, terra cotta pipes get all out of alignment, without problems from roots, etc. To follow these pipes with a pipe being installed inside them, I would think that the pipe that is inserted would be up/down and sideways while following the crooked terra cotta that it was pushed through! If the terra cotta pipe was sloped down and then there was a spot where it had been pushed up out of alignment and then back down, that would form a "Belly" in the pipe or basically a running trap in the line. As debris flowed down the line to that Belly, the debris would slow its travelwhile climbing the raised portion of the pipe. If this happens, some of the debris would stay in the Belly and after a while would stop more and more from going up the raised portion of the pipe. This would result in a stoppage that would require a plumber and a sewer machine to clear for you, like you are having done currently, except it wouldn't be caused by roots!
I am interested in learning more about this proceedure. Could you point me to the name of the proceedure so that I might investigate it further?
Here in my area, one company is doing something similar with waterlines that have been installed under the concrete floors of houses that have developed holes in them. The run a machine through them and coat them with some kind of liquid rubber compound that seals the leaks. Sort of like putting sealant in a automobile tire.
Dick
