So have my Water issue "solved" , Have found out through trial and more trial that the pump while dry camping pulls water from both tanks. When I filled last time water coming out of the front vent check the gauge says full ok should be good stopped carry on. The issue was my gauge said 1/3 of a tank after 4 days and I could not get the pump to prime ,kept sucking air and spurts would come out of the faucet. So got home filled both tanks ,until water coming out of both vents, try pump ,system pressurized normally, dump rear tank, gauge still says full ,try pump NO ,starts sucking air and will not pressurize, so now know both tanks must be full and as the pump draws the water down from the two. The gauge will indicate correctly as it suctions at the same rate from the 2 tanks. The only thing I do wonder if there is a crossover between the 2, and if there is how high up is it on the tank ,or how big is it. Regardless another GD mystery (well to me) solved.