Where are the vent pipes? (AKA: Things That Should Be in the Manual)

[Silver Goose]

I believe code requires the vents, but I don't believe there is a requirement that they exit the roof separately. In my previous SOB, they were joined in a cavity behind the shower and there was only one vent topside. In my present AS, each vents separately to the roof. For some layouts it may be easier to simply run 2 stacks to the top. Both trailers used the vacuum breakers in the bath and kitchen sinks under the counters.