Originally Posted by
madpogue
As long as the sprinkler is running, the water in the pipes won't freeze. And maybe that's why they were running it; they couldn't find the place to shut it off far enough upstream to keep it from freezing, so they just left it running.
I don't think they're that smart and it is just on a timer that runs regardless of weather / temperature. I've seen it drain into their parking lot before creating an ice rink. I think it's actually a hose running to a sprinkler head as opposed to an underground pipe system.