[bncinwv]

You might be able to isolate the location of the fresh water tank by looking at the plumbing beneath the rig. The black tank and the two gray tanks will have drains leading to the dump valve that should be visible beneath the rig. That will give you an indication of where those tanks are, any area left over should be about where the fresh water tank is located, the low point drain on ours only sticks down about an inch below the underbelly.
Bingo