Disconnect or flip the breaker while you're working on it, then it's not dangerous at all, and you won't get a face full of water when it trips on with the pipe disconnected because you bumped the float.
Once it's properly connected, as long as the insulation is fine, there's no harm being down there, though I assure you, you can hear the backflow preventer working from anywhere in the house (it's a solid thud, or at least ours was).
