Lining a pipe to septic

So the smoke test showed no leaks in the house, but a camera run through the pipe between the house and the septic tank showed that the 4' sections of cast iron are offset at just about every joint, from 70 years of settling and shifting. So that's where the smells in the yard are coming from, and probably the smells in the basement as well -- seeping through the masonry foundation.

So do I need to dig the whole thing up and re-lay new pipe? Or is there a way to line the existing 4" pipe?

Thanks.

pipe

1. HOW can cast iron pipe offset every joint if it were installed even slightly correctly?
2. If the pipe is offset, the lining would be offset.
3. Water flows downwards, and odors find the easiest exit.
4. If you have a vent out the roof, the odors would have a much easier time escaping there, than by trying to waft up through several feet of packed soil. (Often too hard for even a shovel to penetrate it.)
5. You diagnosis may be correct, but logic questions it.

With the pipes offset, if they leak gas, they also leak the sewage, and the combination means your entire septic system isn't functioning as designed...who knows what else will show up if you fix the lines to the tank, but I think you need to start there.

Winton, these would have been excellent questions to ask whoever did the smoke test and camera for you. Not trying to be a smart alec but you know what I mean¿