Leaking Anti-Siphon Vac Breaker

One of my outside faucets has a Muellar #888-183 AntiSiphon Vac Breaker. It looks like a simple enough mechanism but I cannot get it to stop leaking water from the air vents. I have tried replacing it and the same thing happens. This was not happening before and only began to leak after I disconnected a nozzle from the attached hose to the faucet.
What should I be doing.
Thanks for a reply.

If you place the sprayer back on the hose will it leak?
If your hose is higher than the sill cock it will leak out the vac breaker.
If you place the hose end on the ground it will drain out the hose.
My wife was a bit surprised the first time this happened. She thought she broke something.