Agree to Mr.Michael,

Even demi-water can remove the wall thickness due to unexpected internal fluid effect such as cavitation or else. Sometime it might be covered by margin between nominal thickness and minimum thickness, but often it doesn't.

Mr. Dave, what you mentioned above is that CAESAR II deduct corrosion allowance even we set the basic code is ASME B31.1 not like the old post that I mentioned?

I assume you meant we turn on the 'all case corroded' option.