Q."Why do many codes require vacuum breakers on hose bibbs?" A. There is a very small chance that you could have your hose in a puddle of dirty water while the water main (or well pump) is shut off or the water main/line broken. Then a negative pressure could arise and suck this potentially bacteria laden or toxic water back into the water main. Yes, it is a slim chance but it can and does happen. Vacuum breakers prevent the water from being able to be sucked back into the hose. Also, sometimes people use submersible pumps which lay in non potable water.
Q."Will these valves (hosebibbs) and vacuum breakers hold up to freezing (not break)?" A. Any water in ANY brand of faucet (even if the walls are many times as thick as what we offer) will break if subjected to freezing conditions. The strength of water expanding during freezing is incredible. If water is left in the hose bibb or vacuum breaker during a freeze, you always run the risk of breakage. If you are in an area where freezing is a concern, we recommend installing only freeze proof hose bibbs, which we offer here.