what is that you used and how did you connect it to the faucet?

The reason it sprays you is that the little rubber goodie inside that's suppose to prevent back-flow probably rotted and quit working about 3 years after the house was built. They don't spray like that when they're new.

It's a really useless device, designed primarily to make rich the guy who invented it and then convinced some bureaucrat to force you to buy it. Think about it -- in order for some nasty bug to sneak from your hose all the way into your stomach, it has to somehow get past a closed hose bib valve, or swim upstream a distance equivalent to you walking to the moon -- only it has to swim through chlorinated water designed to kill it.

The uselessness of this device explains how hundreds of millions of people somehow survived hose bibs prior to the invention of the backflow preventer -- and still do, in places where they aren't required by code.