Thinking of putting in larger fresh water tank

After you fill the new tank, if you notice that it is sagging, you can put in a cross brace underneath it to help support it. I had to do this on my original tank -- the sag meant that I was dragging around ten gallons of extra water that I could not use because the pickup tube for the pump was above the low point of the tank.

Good luck with this project -- let us know how it goes!