I was a plumber for many years and owned and used a small electric jetter that was a a great tool, especially for sinks and laundry drain cleaning. Now I am a maintenance manager in a nuclear plant. We have tools/services called "hydrolazing" that is essentially the same but a much higher pressures to clean thoroughly the inside of pipes and vessels of rust and radioactive contamination. If I wanted to thoroughly clean to "like new" condition old cast iron drains under the basement floor, or overhead in the basement what would be a proposed maximum "safe" pressure to use? Understand, the equipment I have available to me is capable of cutting concrete like it wasn't even there, and could blast rotten old cast clean out of the ground. I don't mind to work the head back and forth several times and clean at a controlled rate to save the pipe walls. Would the proposed pressure be the same for sched 40 PVC? I will be able to seesnake the line during and after cleaning to check progress and quality. Before anyone asks, the machine I have available is capable to 26,000 psi.