Crumbling Pipes

We noticed some water under the kitchen sink, and when I checked the leaky pipe that was the cause . . . it crumbled under my finger. Literally crumbled, as if it was made of eggshells. Since it was put in, perhaps as early as 1892, the pipe has worn to the thickness of card stock. When that pipe was removed, the same thing happened to the pipes around it, and then to the vent pipe next to them both. In the end, the repair took a fair chunk of change and will stretch over two (part-time) days. Thank you 120 year old home, for creating yet another pit where I can toss my cash.