The PVC evacuation pipe from my toilet is leaking a little bit. The part of the pipe that is leaking is buried inside concrete. I am trying to find a way to fix the leak from inside the pipe, that is without having to break the concrete to access the pipe. I have acces to the open end of the pipe about 1 meter away from where the leak is.
I ended up pouring some very liquid mix of waterproof cement down the pipe and catching it again at the exit, it seems that is filled the little cracks inside the pipe. It's been a few weeks of testing by pouring water down and I don't see any leaks anymore. I have to specify that the pipe was horizontal and the cracks on the bottom part of it, that allowed the cement to fill the cracks.
The only way that I know of to repair this kind of damage without replacing the pipe is to have an epoxy lining installed.
What this essentially will do is add a tough epoxy coating to the entire pipe from the inside. This is something you would need a specialist for. The tools and materials are not readily available to a homeowner.
An epoxy liner is not 100% foolproof. There can be mistakes made with the application, and the existing pipe may continue to degrade and cause further leaks. The best way to fix this problem permanently would be to completely replace the new pipe.