I think what I'm going to do at this point after reading all the horror stories related to the high cost black plastic valve that apparently the bulk of RV manufacturers install, is take it out and get a real one. I'm going to take the valve to a local plumbing supply house, let them see the fine piece of American plastic craftsmanship and see what they can come up with for a backflow preventer and vacuum breaker. I know other members have installed Watts #7 backflow preventers and that may be what I end up with, but I would like to try to keep the vacuum breaker involved in the system. I figure someone who designs these systems knows more than me and there's a reason why there is a backflow preventer and vacuum breaker there.
I did notice when I took it out that the vacuum breaker is pretty much a joke. It's a piece of white plastic that moves up and down inside the cylinder of the valve body. As soon as it gets some use it's going to wear and that's where the leaks are probably coming from that a lot of people are complaining about.
2015 Forester 2301 - Chevy
Skip & Deb - Denmark, ME & Delray Beach, FL