The bypass valve for the hot water tank should be behind the HW tank and has it's own shut off. There has to be another shut off valve on the cold water (blue) going in the tank and on the hot water (red) coming out of the tank. The bypass valve/pipe is located just before those valves and should be in the closed position during normal use. When you winterize that bypass valve gets opened and the other two valves get closed to prevent antifreeze from entering the HW tank. I found goggle/you-tube videos very helpful and informative for anything RV related. I havn't done any of this RV stuff yet but I've got a pretty good idea thanks to you-tube and this forum
