Thanks so much everyone for your replies....
The whole bottom is sealed so I could not see the size/s of the pipes and both handles are black. I did get a 45 degree clear extension for the pipe and test dumped the farthest left one - it was indeed the grey tank.
I love the duck tape idea - Thanks
I've installed it behind my grey handle.
I do also have a 3rd, galley tank and am very surprised they did not somehow connect both grey tanks for ease of dumping.
I do Love the new rig though. Took it on the first trip to Hot Springs on derby weekend and it handles great.
Again, thanks for all you thoughts.