I can walk through any subdivision here and look at the backflow preventers and probably 50% of them have had damage at one time. Probably more than 50%. Either the ball valves have been replaced, copper or PVC has a patch, homeowner shoved silicone up into the bonnet area, the top to the PVB is missing which indicates they've repaired it and lost the cover. When I'm bored and driving I will look on the sides of homes for the BFP and try to see damage. Saw 2 broken bonnets yesterday, and another that was leaking water somewhere. A little preventive maintenance goes a long way. I have 3 copper or BFP repairs to do still, but I'm putting it off until tomorrow.