The leakage in a 3400rl around the steps leaking onto the vinyl????
I can't find your post anywhere.
You asked about what a vacuum breaker was, I have info. on that topic.
Also, I wanted to tell you that I added water to my fresh water tank with the valve in the service bay, my vacuum breaker stuck up behind the shower, I guess, (there is one up there somewhere, maybe other members know about it)because I had water all over the floor by the steps, may be the same problem with yours. I know you stated it happened when raining, but this may be concindence...
Here are some links for you.
(Besides, I think you offered a quarter for the solution...)
http://www.filterchem.com/vacuum-breaker-valves.cfm
http://www.watts.com/pro/_products_s...=65&parCat=102
http://en.wikipedia.org/wiki/Atmospheric_vacuum_breaker