I have a galvanized 6". Currently drained 60's pond. I used a GoPro to run in it and have a look. No holes yet kind of hard to know how thin it is just like the above comment. It's got holes on the outlet though. It looks like they coated the galvanized with tar perhaps once upon a time.

Lets say he and I want close the old pipe. Can you cap it at the end and put concrete in from the top?

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