Originally Posted by PistolPete
That isn't true. As long as both ends are in the water and the water is pumped or sucked out it will be fine.
This would require a good knowledge of physics and a good calculator.
The physics behind it are that gravity is going to make the water equalize. So if tank A's water level is 5 feet above the ground, and tank B's water level is 4 feet above the ground, the water is going to probably siphon 6 inches of water out of tank A into tank B making both water levels 4.5 feet.
Now knowing that, if you wish to put the tank on separate levels you have to cancel out the siphon with a pump that puts the water in the higher tank with the same rate of flow or eventually one will overflow.
Not impossible, but not easy.