I Have a Vac.Breaker installed on each of my two water lines going to the back yard and the garage.These breakers keep leaking water. My question is do I need them there or can I remove them, and what is their function. Thank you.

They do tend to leak a bit since the diaphragm gets some debris in them and won't seal. They will also bleed out the line and leak a bit when the water is turned off. It is probably code in your area to have them. They are backflow preventers and are there to prevent hazardoua materials from getting sucked back into the main line. For example, if you are using a hose sprayer to spray some poison and the city water pressure fails, it could suck the material back into the city supply. Are they removed? All the time. They usually have a set screw that locks them onto the threads of the bib. Key is to turn the water off at the hose bib and not at the nozzel.

What you say makes sense.
Thank you.