I have a customer with an older sub panel in the guest house that was installed with SEU in RMC underground and under a patio for a total of 170 feet. Now they are selling and the HI wrote up the 3 wire sub panel. I told them we need a new feeder but they want me to use the old RMC for the grounding. It is probably 30 years old, not wrapped or coated and rusted where it enters the ground. I told them I wouldn't do it for liability reasons, even if it tests good now how much longer can it last? I have seen this stuff disintegrate after less than 20 years in our high alkali soil. Of course they will probably find someone else to do it but I feel comfortable that I made the right call, what would you do?