We have a backup hot water baseboard boiler system for heat in the house. Part of that system includes a pressure limiter and backflow prevention device. The backflow device is prone to leaking over time and ours did just that. This is problematic in that the leaking requires more water into the system which, in turn, leads to the pump running which draws the batteries down which makes the generator run.
So I had to find a new part. I ordered one, but the specific set up on it was just different enough that I'd have had to sweat pipe in a close location. Not really my favorite thing, setting the house on fire. :D
It took me almost a year of hunting to find the exact same brand name and configuration for the part. And now I have it. This morning I'll put it on and the world will rejoice.