Warehouse fire sprinkler pipe corrosion (leak-driven oxygen makeup)

Large warehouse's entire fire sprinkler system was fully occluded with rust. Root cause: a tolerated leak introduced makeup water (and fresh oxygen) to what should have been a closed system. All piping required replacement.

One time I got a two-inch diameter pipe, maybe one and a half inch, completely occluded with rust. This had been in a big warehouse, and they told me that all the pipes — this is a huge warehouse — everything was occluded. They were going to have to replace all the steel piping in their fire protection system. They wanted to do some tests. I called them up and said, you guys have a leak in your system? Oh yeah. They had a leak, a stream of water that they had just running into a drain. They'd had it for a couple of years and they didn't fix it. I said, well you're going to have to replace all your piping because of that stream of water — the makeup water is bringing oxygen into the system and corroding it. You were supposed to have a closed system that didn't have a lot of makeup water. You can tolerate a little makeup water — you always have a little bit of oxygen — but you don't just let a leak go. They just didn't bother to fix this thing. I said, well, too bad, you've got to replace all the pipes. An awful lot of iron oxide.