Need carrying capacity explaned

Gadget Guy wrote:
A lot will disagree with me but I want to be able to legally carry:
a) full water tank
c) full gray tank
d) full black tank

Why do you want a full gray tank, a full black tank, and a full fresh water tank??? I want a full water tank and both black and gray tanks to be empty. And as the fresh water goes down, the black and grey water go up. When you add fresh water, you empty your waste black and grey water tanks. The load balances out much better that way! AND if you fresh water tank is full, and the waste water tanks are full, I can't use my fresh water!!! What good is that??