I can't work yet, but, once when I was helping my dad run a cable line along a black iron drain line, he was driling through the wall to the garage (the target room was right next to a bathroom and the pipes came in through the bedroom's closet), half way through drilling, his drill stops, then the upstairs toilet flushes, then, we realize that he drilled into the bathroom's drain line. Yuck! Thankfully, we had to leave the next day, next time we go though, there's a new piece of pipe welded in, and new furniture where the pipe went through the wall.
Ian A
