I'm installing a PVC french drain in the basement. It had to cross the 50-year-old cast iron waste line which needed a deep excavation around it. I don't want to put the soil back in the large hole because that won't be very supportive for the foundation footing (like undisturbed soil) so I want to pack gravel in.

My concern is whether the gravel will accelerate the pipe rusting away in that area. The gravel probably will hold more water in the voids than the surrounding soil. Air too.

Any thoughts on this causing the pipe to corrode through faster?

Thanks, guys.

there must be ground water around the pipe in order for it to corrode.
I don't believe there is enough moisture content in mother earth to harm the pipe.
this is just my humble opinion.

We have groundwater, that's why we need the french drain. My concern is the deep "well" now around the pipe will hold it.



Edited 1 times.

If you have groundwater, it is already around the cast iron pipe.