Here is an interesting one for you: I bought a house that I have been in for a couple years and instead of the sanitary piping being PVC or cast iron, it is all copper. I know the lime in concrete can eat thru copper but how about sanitary waste? Also the sanitary main goes over the foundation instead of thru it under the frost line and it goes down the outside into the ground to the septic tank. I live on the East Coast and surprisingly this does not freeze up in the winter. Should this all be replaced or is this of the idea of "If it ain't broken, don't fix it"?