Hello guys, this is my first post on this website, however, I have been a longtime reader. I read most of the posts on the irrigation forum and find that most of you guys have a tremendous amount insight. Just to give you some background on me: I am not an irrigation expert by any means, but I did work on an installation crew for one of Atlanta's large irrigation companies during the summer for 7 years when I was in High School and College. I am no longer in the irrigation business, but I enjoy helping neighbors and friends do small irrigation repairs/rehabs/installations the appropriate way. My question is related to back-flow prevention regulations in Georgia. My understanding is that the International Plumbing Code requires that the potable water supply to lawn irrigation systems shall be protected against back-flow by an atmospheric vacuum breaker, a pressure-type vacuum breaker, a reduced pressure principle back-flow preventer and (as of a few years ago) a double check back-flow prevention assembly. The Georgia Plumbing Code basically mirrors the same principles: 608.16.5 Connections to lawn irrigation systems: The potable water supply to lawn irrigation systems shall be protected against back-flow by an atmospheric-type vacuum breaker, a pressure-type vacuum breaker, a double-check back-flow prevention assembly or a reduced pressure principle back-flow preventer. A valve shall not be installed downstream from an atmospheric vacuum breaker. Where interconnected chemical dispensers are used in conjunction with lawn irrigation systems, the potable water supply shall be protected against back-flow by a reduced pressure principle back-flow preventer. All of the residential irrigation system installations that I have seen done in the Metro Atlanta area (for a number of years) have all been installed using a "Dual Check Valve", which seems to be much different than the minimum standard of a Double Check Valve Assembly. As a matter of fact, I have never seen even a Double Check Valve Assembly installed on a residential job in the State of Georgia, much less any of the other back-flow types. For those of you in the State of Georgia: have you seen the "Dual Check Valve" installations? How do Companies get away with this? Sorry for the long post, but I appreciate your responses.